str_pad

(PHP 4 >= 4.0.1, PHP 5, PHP 7, PHP 8)

str_pad — 使用另一个字符串填充字符串为指定长度

说明

str_pad ( string $input , int $pad_length , string $pad_string = " " , int $pad_type = STR_PAD_RIGHT ) : string

该函数返回 input 被从左端、右端或者同时两端被填充到制定长度后的结果。如果可选的 pad_string 参数没有被指定，input 将被空格字符填充，否则它将被 pad_string 填充到指定长度。

参数

input

输入字符串。

pad_length

如果 pad_length 的值是负数，小于或者等于输入字符串的长度，不会发生任何填充，并会返回 input 。

pad_string

Note:

如果填充字符的长度不能被 pad_string 整除，那么 pad_string 可能会被缩短。

pad_type

可选的 pad_type 参数的可能值为 STR_PAD_RIGHT，STR_PAD_LEFT 或 STR_PAD_BOTH。如果没有指定 pad_type，则假定它是 STR_PAD_RIGHT。

返回值

返回填充后的字符串。

范例

Example #1 str_pad() 范例

<?php
$input = "Alien";
echo str_pad($input, 10);                      // 输出 "Alien     "
echo str_pad($input, 10, "-=", STR_PAD_LEFT);  // 输出 "-=-=-Alien"
echo str_pad($input, 10, "_", STR_PAD_BOTH);   // 输出 "__Alien___"
echo str_pad($input,  6, "___");               // 输出 "Alien_"
echo str_pad($input,  3, "*");                 // 输出 "Alien"
?>

User Contributed Notes

robertwhishaw at gmail dot com 07-Jun-2020 03:44
Incrementing or decrementing numbers in PHP is easy with the ++ and -- operators but it can be difficult to set the precision of the numbers. The str_pad() can be useful for concatenating a string to the beginning or end of the incrementing number to simulate a different precision.

Good example, we want to increment 001 to 002, 003, 004:

$numbers = [];

for($i = 1; $i <= 4; $i++){
    $numbers[] = str_pad($i, 3, '0', STR_PAD_LEFT);
}

print_r($numbers);

$numbers[0] => '001',
$numbers[1] => '002',
$numbers[2] => '003',
$numbers[3] => '004',

Bad example, we want to increment 001 to 002, 003, 004 but if we set $i = 001 in the for() loop to start with, 001 will be converted to 1 and the incrementing will return: 1, 2, 3, 4 etc...

$numbers = [];

for($i = 001; $i <= 4; $i++){
    $numbers[] = $i;
}

print_r($numbers);

$numbers[0] => 1,
$numbers[1] => 2,
$numbers[2] => 3,
$numbers[3] => 4,
neo_selen 04-Jun-2020 02:11
you can use str_pad to display an integer with a fixed amount of digits, like that:
0002
0003
...
0100

by just writing

<?php
    for ($i=0;$i<10000;$i++){
        echo str_pad($i,4,'0',STR_PAD_LEFT)."\n";
    }
?>

i set 4 digits (see parameter #2), but you can set any fitting your needs.
babak dot asad73 at gmail dot com 02-Jun-2020 09:07
how to add some 0 before numbers
for example 5  ===> 005

do something like this:

echo str_pad(5,3,0,STR_PAD_LEFT); // result 005

echo str_pad(4,6,0,STR_PAD_LEFT); // result 000005
NOSPAM dot php at my dot jrklein dot com 07-Dec-2019 06:53
str_pad() can provide sufficient "zero padding" when using block ciphers and manual padding with openssl_encrypt() and similar.

The example below will pad the 6 character text "Secret" with two \x00 characters and return 8 characters of data. Substitute your plain text and block size as needed.

<?php
$text = "Secret";
$block_size = 8;
$length = ceil(strlen($text) / $block_size) * $block_size;
$data = str_pad($text, $length, "\x00");
Kirill Fuchs 06-Aug-2017 09:32
sprintf() is not always faster... It certainly scales a lot better then str_pad so when running a benchmark that pads 10k characters,  sprintf will come out on top. But if you benchmarked a more real world scenario, it seems str_pad comes out the clear winner.

$sTime = microtime(true);
$count = 5;
$s = sprintf("%'\n5s", "\n");
$eTime = microtime(true);
echo 'sprintf ran in ' . (($eTime - $sTime) * 1000) . ' milliseconds' . "\n";

$sTime = microtime(true);
$s = str_pad("\n", 5, "\n");
$eTime = microtime(true);
echo 'str_pad ran in ' . (($eTime - $sTime) * 1000) . ' milliseconds' . "\n";

sprintf ran in 0.015974044799805 milliseconds
str_pad ran in 0.0059604644775391 milliseconds
pulketo at gmail dot com 12-Jun-2017 04:35
// Columnizer: add padding into text columns according maximum column size.
// sample input:
$a='[1515] -> ID=1515 / post_date=2012-06-18 04:48:47 / post_name=review-terminatrix-by-sfam
    [177] -> ID=177 / post_date=2017-05-12 12:12:03 / post_name=review-the-terminator-by-sfam
    [228621100] -> ID=2286 / post_date=2012-06-18 04:48:32 / post_name=terminator-3-rise-of-the-machines-2003';

function columnize($input, $separator=" "){
    $lines = explode("\n", $input);
    foreach ($lines as $k=>$line){
      $r[$k] = explode(" ", trim($line));
    }
    // print_r($r);
    $nc = sizeOf($r[0]);
    // echo $nc;
    for($i=0;$i<$nc;$i++){
      $col[$i] = array_column($r, $i);
      }
    // print_r($col);
    for ($i=0;$i<sizeof($col);$i++){
      $maxlen = max(array_map('strlen', $col[$i]));
      $tam[$i]=$maxlen;
      // echo "$i:$maxlen".PHP_EOL;
      $cs[$i]=$maxlen;
    }
    // print_r($cs);
    $o="";
    for ($r=0;$r<sizeOf($lines);$r++){
      for ($c=0;$c<sizeof($cs);$c++){
        $o.= str_pad($col[$c][$r], $cs[$c]+2, " ", STR_PAD_RIGHT );
      }
      $o .= PHP_EOL;
    }   
    return $o;
  }

echo $columnize($a);
// will output text nicely in columns :)
gtwizard 10-Jan-2017 02:52
sprintf is faster

$sTime = microtime(true);
$s = sprintf("%'-1000000s", '-');
$eTime = microtime(true);
echo 'sprintf ran in ' . (($eTime - $sTime) * 1000) . ' milliseconds' . "\n";

$sTime = microtime(true);
$s = str_pad('-', 1000000, '-');
$eTime = microtime(true);
echo 'str_pad ran in ' . (($eTime - $sTime) * 1000) . ' milliseconds' . "\n";

//result
sprintf ran in 2.0260810852051 milliseconds
str_pad ran in 26.59797668457 milliseconds
Anonymous 11-Mar-2016 10:25
Here is the mcinp's version of mb_str_pad bugfixed:

<?php
function mb_str_pad($input, $pad_length, $pad_string=' ', $pad_type=STR_PAD_RIGHT,$encoding='UTF-8'){
        $mb_diff=mb_strlen($input, $encoding)-strlen($input);
        return str_pad($input,$pad_length-$mb_diff,$pad_string,$pad_type);
    }
?>

Still working correctly only if $pad_string is non-multibyte string
Anonymous 19-Jul-2015 11:13
For simple padding, you can use sprintf, which is faster:
see http://php.net/sprintf Example #5 "Specifying padding character"
mcinp 29-Jan-2015 04:04
a different, more robust multibyte version of str_pad that works correctly only if $pad_string is non-multibyte string

function my_mb_str_pad($input, $pad_length, $pad_string=' ', $pad_type=STR_PAD_RIGHT,$encoding='UTF-8'){
    $mb_diff=mb_strlen($str, $encoding)-strlen($string);       
    return str_pad($input,$pad_length+$mb_diff,$pad_string,$pad_type);
}
wes at nospamplsexample dot org 28-Nov-2014 06:29
multibyte version:

<?php
function mb_str_pad($str, $pad_len, $pad_str = ' ', $dir = STR_PAD_RIGHT, $encoding = NULL)
{
    $encoding = $encoding === NULL ? mb_internal_encoding() : $encoding;
    $padBefore = $dir === STR_PAD_BOTH || $dir === STR_PAD_LEFT;
    $padAfter = $dir === STR_PAD_BOTH || $dir === STR_PAD_RIGHT;
    $pad_len -= mb_strlen($str, $encoding);
    $targetLen = $padBefore && $padAfter ? $pad_len / 2 : $pad_len;
    $strToRepeatLen = mb_strlen($pad_str, $encoding);
    $repeatTimes = ceil($targetLen / $strToRepeatLen);
    $repeatedString = str_repeat($pad_str, max(0, $repeatTimes)); // safe if used with valid utf-8 strings
    $before = $padBefore ? mb_substr($repeatedString, 0, floor($targetLen), $encoding) : '';
    $after = $padAfter ? mb_substr($repeatedString, 0, ceil($targetLen), $encoding) : '';
    return $before . $str . $after;
}
?>
Marjune 17-Nov-2014 03:45
since the default pad_type is STR_PAD_RIGHT. using STR_PAD_BOTH were always favor in the right pad if the required number of padding characters can't be evenly divided.

e.g

<?php

echo str_pad("input", 10, "pp", STR_PAD_BOTH ); // ppinputppp
echo str_pad("input", 6, "p", STR_PAD_BOTH ); // inputp
echo str_pad("input", 8, "p", STR_PAD_BOTH ); //pinputpp

?>
qeremy [atta] gmail [dotta] com 20-Jan-2013 01:44
A proper unicode string padder;

<?php
mb_internal_encoding('utf-8'); // @important

function str_pad_unicode($str, $pad_len, $pad_str = ' ', $dir = STR_PAD_RIGHT) {
    $str_len = mb_strlen($str);
    $pad_str_len = mb_strlen($pad_str);
    if (!$str_len && ($dir == STR_PAD_RIGHT || $dir == STR_PAD_LEFT)) {
        $str_len = 1; // @debug
    }
    if (!$pad_len || !$pad_str_len || $pad_len <= $str_len) {
        return $str;
    }
   
    $result = null;
    $repeat = ceil($str_len - $pad_str_len + $pad_len);
    if ($dir == STR_PAD_RIGHT) {
        $result = $str . str_repeat($pad_str, $repeat);
        $result = mb_substr($result, 0, $pad_len);
    } else if ($dir == STR_PAD_LEFT) {
        $result = str_repeat($pad_str, $repeat) . $str;
        $result = mb_substr($result, -$pad_len);
    } else if ($dir == STR_PAD_BOTH) {
        $length = ($pad_len - $str_len) / 2;
        $repeat = ceil($length / $pad_str_len);
        $result = mb_substr(str_repeat($pad_str, $repeat), 0, floor($length))
                    . $str
                       . mb_substr(str_repeat($pad_str, $repeat), 0, ceil($length));
    }
   
    return $result;
}
?>

Test;
<?php
// needs ie. "test.php" file encoded in "utf-8 without bom"
$s = '...';
for ($i = 3; $i <= 1000; $i++) {
    $s1 = str_pad($s, $i, 'AO', STR_PAD_BOTH); // can not inculde unicode char!!!
    $s2 = str_pad_unicode($s, $i, '??', STR_PAD_BOTH);
    $sl1 = strlen($s1);
    $sl2 = mb_strlen($s2);
    echo  "len $sl1: $s1 \n";
    echo  "len $sl2: $s2 \n";
    echo  "\n";
    if ($sl1 != $sl2) die("Fail!");
}
?>

Output;
len 3: ...
len 3: ...

len 4: ...A
len 4: ...?

len 5: A...A
len 5: ?...?

len 6: A...AO
len 6: ?...??
...
sergey 12-Oct-2011 02:45
You can use trim functions for clearpad string:

ltrim("0001230", "0") -> 1230
rtrim("0123000", "0") -> 0123
trim("0012300")     -> 123
gene at swipesy dot com 24-Sep-2011 09:18
This is how I pad using &nbsp; :

str_replace(" ", "&nbsp;&nbsp;", str_pad($foo, 10, " ", STR_PAD_LEFT))

Seems to work well using two &nbsp; tags for each character added, at least for my use. YMMV.
Kari &#34;Haprog&#34; Sderholm 21-Mar-2009 06:43
Here's a quick and simple way to make an mb_str_pad function that works when you have correctly set your internal encoding.

I'm not sure how well this works in all possible scenarios but atleast it worked for me using UTF-8 as internal encoding and using this function on strings containing scandinavian characters "??????" that are double byte in UTF-8.

<?php
function mb_str_pad($input, $pad_length, $pad_string=' ', $pad_type=STR_PAD_RIGHT) {
    $diff = strlen($input) - mb_strlen($input);
    return str_pad($input, $pad_length+$diff, $pad_string, $pad_type);
}
?>
matrebatre 16-Oct-2008 11:28
Here is a simple function to convert numbers into strings like this:

0 => 0000
1 => 0001
20 => 0020
432 => 0432

<?php

function number_pad($number,$n) {
return str_pad((int) $number,$n,"0",STR_PAD_LEFT);
}

?>

$n indicates how many characters you want.
bxi at apparoat dot nl 20-Mar-2008 06:17
In case you want to pad 2 strings together with a character you can use:

<?php
function pad_between_strings($string1, $string2, $length, $char = " ") {
    $fill_length = $length - ( strlen($string1) + strlen($string2) );
    return $string1 . str_repeat($char, $fill_length) . $string2;
}
?>
Spudley 18-Jul-2007 08:47
Warning: If your string includes non-ascii characters (eg the British pounds sign), str_pad() will treat these as two characters when calculating the padding.

So for example:
<?php
str_pad($currency_symbol.$showtottopay,12," ",STR_PAD_LEFT);
?>
will produce a different length string depending on whether $currency_symbol is pounds or dollars.

Hope this helps someone -- it caused me a lot of problems with misaligned columns in my invoices until I worked it out.
christian dot reinecke at web dot de 01-Apr-2007 10:43
Fills the first argument (mostly a number, f.e. from a <select> loop to display a date or time) with zeroes.

<?php
function zerofill($mStretch, $iLength = 2)
{
    $sPrintfString = '%0' . (int)$iLength . 's';
    return sprintf($sPrintfString, $mStretch);
}
?>

sprintf() is indeed faster than str_pad.
Silvio Ginter (silvio dot ginter at gmx dot de) 15-Nov-2005 08:43
Hello,

for anyone who needs this, I wrote this extension to str_pad. For details, just look at the comments.

<?php

$string = 'this is a test';
$oldLen = strlen($string);
$direction = STR_PAD_BOTH;
echo $string.'<br>';
echo str_const_len($string, 101, '#', $direction).'<br>';
echo $string.'<br>';
echo str_const_len($string, $oldLen, '#', $direction).'<br>';
echo $string.'<br><br>'."\n";

   
   
/*     This function is an extension to str_pad, it manipulates the referenced
    string '$str' and stretches or reduces it to the specified length. It
    returns the number of characters, that were added or stripped. */
function str_const_len(&$str, $len, $char = ' ', $str_pad_const = STR_PAD_RIGHT) {
    $origLen = strlen($str);
    if (strlen($str) < $len) {     /* stretch string */
        $str = str_pad($str, $len, $char, $str_pad_const);
    }
    else {                         /* reduce string */
        switch ($str_pad_const) {
            case STR_PAD_LEFT:
                $str = substr($str, (strlen($str) - $len), $len);
                break;
            case STR_PAD_BOTH:
                $shorten = (int) ((strlen($str) - $len) / 2);
                $str = substr($str, $shorten, $len);
                break;
            default:
                $str = substr($str, 0, $len);
                break;
        }
    }
    return ($len - $origLen);
}
?>
private dot email at optusnet dot com dot au 10-Aug-2005 05:04
I wrote these 3 functions that live in a library i include in every programme. I find them useful, and the syntax is easy.

<?php

$str = "test";

function str_pad_right ( $string , $padchar , $int ) {
    $i = strlen ( $string ) + $int;
    $str = str_pad ( $string , $i , $padchar , STR_PAD_RIGHT );
    return $str;
}
   
function str_pad_left ( $string , $padchar , $int ) {
    $i = strlen ( $string ) + $int;
    $str = str_pad ( $string , $i , $padchar , STR_PAD_LEFT );
    return $str;
}
   
function str_pad_both ( $string , $padchar , $int ) {
    $i = strlen ( $string ) + ( $int * 2 );
    $str = str_pad ( $string , $i , $padchar , STR_PAD_BOTH );
    return $str;
}

echo str_pad_left ( $str , "-" , 3 ); // Produces: ---test
echo str_pad_right ( $str , "-" , 3 ); // Produces: test---
echo str_pad_both ( $str , "-" , 3 ); // Produces: ---test---
?>

Hope this can help someone!
zubfatal <root at it dot dk> 27-Mar-2005 09:28
<?php
    /**
     * str_pad_html - Pad a string to a certain length with another string.
     * accepts HTML code in param: $strPadString.
     *
     * @name        str_pad_html()
     * @author        Tim Johannessen <root@it.dk>
     * @version        1.0.0
     * @param        string    $strInput    The array to iterate through, all non-numeric values will be skipped.
     * @param        int    $intPadLength    Padding length, must be greater than zero.
     * @param        string    [$strPadString]    String to pad $strInput with (default: &nbsp;)
     * @param        int        [$intPadType]        STR_PAD_LEFT, STR_PAD_RIGHT (default), STR_PAD_BOTH
     * @return        string    Returns the padded string
    **/
    function str_pad_html($strInput = "", $intPadLength, $strPadString = "&nbsp;", $intPadType = STR_PAD_RIGHT) {
        if (strlen(trim(strip_tags($strInput))) < intval($intPadLength)) {
           
            switch ($intPadType) {
                 // STR_PAD_LEFT
                case 0:
                    $offsetLeft = intval($intPadLength - strlen(trim(strip_tags($strInput))));
                    $offsetRight = 0;
                    break;
                   
                // STR_PAD_RIGHT
                case 1:
                    $offsetLeft = 0;
                    $offsetRight = intval($intPadLength - strlen(trim(strip_tags($strInput))));
                    break;
                   
                // STR_PAD_BOTH
                case 2:
                    $offsetLeft = intval(($intPadLength - strlen(trim(strip_tags($strInput)))) / 2);
                    $offsetRight = round(($intPadLength - strlen(trim(strip_tags($strInput)))) / 2, 0);
                    break;
                   
                // STR_PAD_RIGHT
                default:
                    $offsetLeft = 0;
                    $offsetRight = intval($intPadLength - strlen(trim(strip_tags($strInput))));
                    break;
            }
           
            $strPadded = str_repeat($strPadString, $offsetLeft) . $strInput . str_repeat($strPadString, $offsetRight);
            unset($strInput, $offsetLeft, $offsetRight);
           
            return $strPadded;
        }
       
        else {
            return $strInput;
        }
    }

?>
bob [at] bobarmadillo [dot] com 03-Dec-2002 09:22
In a lot of cases you're better off using str_repeat if you want to use something like   - it repeats the entire string.

Using str_repeat, I wrote a full string pad function that should closely mimic str_pad in every other way:

<?php
function full_str_pad($input, $pad_length, $pad_string = '', $pad_type = 0) {
 $str = '';
 $length = $pad_length - strlen($input);
 if ($length > 0) { // str_repeat doesn't like negatives
  if ($pad_type == STR_PAD_RIGHT) { // STR_PAD_RIGHT == 1
   $str = $input.str_repeat($pad_string, $length);
  } elseif ($pad_type == STR_PAD_BOTH) { // STR_PAD_BOTH == 2
   $str = str_repeat($pad_string, floor($length/2));
   $str .= $input;
   $str .= str_repeat($pad_string, ceil($length/2));
  } else { // defaults to STR_PAD_LEFT == 0
   $str = str_repeat($pad_string, $length).$input;
  }
 } else { // if $length is negative or zero we don't need to do anything
  $str = $input;
 }
 return $str;
}

$pad_me = "Test String";
echo '|'.full_str_pad($pad_me, 20, ' ')."|\n";
echo '|'.full_str_pad($pad_me, 20, ' ', STR_PAD_RIGHT)."|\n";
echo '|'.full_str_pad($pad_me, 20, ' ', STR_PAD_BOTH)."|\n";
?>
Fahad dot Gilani at anu dot edu dot au 02-Dec-2002 02:22
Basically, *all* of you guys have a 'long' way of padding text with html tags (which includes &nbsp;) You dont even have to do a str_replace... try the following code and this will work with ANY html tag there is out there and you don't have to worry about tag character lengths so on and so forth:
<?
  $text = "This is pretty interesting!";
  $pad_string = "&nbsp;";
 
  //Pad text on both sides
  $text = str_pad($text, strlen($text)+(20*strlen($pad_string)), $pad_string, STR_PAD_BOTH);
  print $text." Dont you think?";
?>
Will produce:
          This is pretty interesting!           Dont you think?

Cheers,
Fahad
mreilly at NOSPAM dot mac dot com 20-Aug-2002 11:23
When provided with a string of characters as the pad value, str_pad uses all the characters as fill, and can leave partial strings. (eg. If the pad value is 'ABC' and it needs 5 characters to pad with, it outputs 'ABCAB'.) This is a problem when you want to pad with non-breaking spaces, the code for which is 6 characters long.

This can be resolved by first padding the string with a single character that won't be found in the strings such as * then doing a str_replace of * with &nbsp;.
pestilenc at hotmail dot com 06-Jun-2002 04:26
For me this worked.
$string = 'help';

#First, str_pad() with unique character.
$string = str_pad($string, 10, "*", STR_PAD_BOTH);
#$string = '***help***';

#Second, str_replace with '&nbsp;'
$string = str_replace("*", "&nbsp;", $string);
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