(PHP 8)
str_starts_with — Checks if a string starts with a given substring
$haystack
, string $needle
) : bool
Performs a case-sensitive check indicating if
haystack begins with needle.
haystackThe string to search in.
needle
The substring to search for in the haystack.
Returns true if haystack begins with
needle, false otherwise.
Example #1 Using the empty string ''
<?php
if (str_starts_with('abc', '')) {
echo "All strings start with the empty string";
}
?>
以上例程会输出：
All strings start with the empty string
Example #2 Showing case-sensitivity
<?php
$string = 'The lazy fox jumped over the fence';
if (str_starts_with($string, 'The')) {
echo "The string starts with 'The'\n";
}
if (str_starts_with($string, 'the')) {
echo 'The string starts with "the"';
} else {
echo '"the" was not found because the case does not match';
}
?>
以上例程会输出：
The string starts with 'The' "the" was not found because the case does not match
Note: 此函数可安全用于二进制对象。
In PHP7 you may want to use:
if (!function_exists('str_starts_with')) {
function str_starts_with($str, $start) {
return (@substr_compare($str, $start, 0, strlen($start))==0);
}
}
AFAIK that is binary safe and doesn't need additional checks.
With credit to Paul Phillips for the original polyfill posted.
If you do not have PHP 8, you can use these functions to get the capability of the new string functions.
But! Remember to use a conditional check to make sure the function is not already defined.
<?php
// source: Laravel Framework
// https://github.com/laravel/framework/blob/8.x/src/Illuminate/Support/Str.php
if (!function_exists('str_starts_with')) {
function str_starts_with($haystack, $needle) {
return (string)$needle !== '' && strncmp($haystack, $needle, strlen($needle)) === 0;
}
}
if (!function_exists('str_ends_with')) {
function str_ends_with($haystack, $needle) {
return $needle !== '' && substr($haystack, -strlen($needle)) === (string)$needle;
}
}
if (!function_exists('str_contains')) {
function str_contains($haystack, $needle) {
return $needle !== '' && mb_strpos($haystack, $needle) !== false;
}
}
?>
This keeps it from breaking in case you upgrade and forget that you added it. This is a good practice generally when using the global scope for your helper functions.
You can use this in PHP versions less than 8.
<?php
function str_starts_with ( $haystack, $needle ) {
return strpos( $haystack , $needle ) === 0;
}