SplFileObject::fgets

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

SplFileObject::fgets — Gets line from file

说明

public SplFileObject::fgets ( ) : string

Gets a line from the file.

参数

此函数没有参数。

返回值

Returns a string containing the next line from the file, or false on error.

错误／异常

Throws a RuntimeException if the file cannot be read.

范例

Example #1 SplFileObject::fgets() example

This example simply outputs the contents of file.txt line-by-line.

<?php
$file = new SplFileObject("file.txt");
while (!$file->eof()) {
    echo $file->fgets();
}
?>

参见

User Contributed Notes

Lucas Bustamante 22-Oct-2021 11:34
I forgot to mention in my previous note about PHP PHP 8.0.10, that you can use $file->current(); $file->next(); as a replacement for $file->fgets(); that works consistently from PHP 5.1 to 8.0.1+ after a seek():

<?php

$file = new SplTempFileObject();

for ($i = 0; $i < 100; $i++) {
    $file->fwrite("Foo $i\n");
}

$file->seek(50);

print_r(array(
    array('line' => $file->key(), 'contents' => trim($file->current()), 'triggerNext' => $file->next()),
    array('line' => $file->key(), 'contents' => trim($file->current()), 'triggerNext' => $file->next()),
    array('line' => $file->key(), 'contents' => trim($file->current()), 'triggerNext' => $file->next()),
));

?>

PHP 5.1 to 8.0.1+:

[
    {
        "line": 50,
        "contents": "Foo 50"
    },
    {
        "line": 51,
        "contents": "Foo 51"
    },
    {
        "line": 52,
        "contents": "Foo 52"
    }
]
Lucas Bustamante 22-Oct-2021 11:19
Notice that the behavior of fgets after a seek changed on PHP 8.0.10, if you seek to line 50 and run fgets, it will give you line 50, while on PHP 5.1~8.0.0 it would give you line 51:

<?php

$file = new SplTempFileObject();

for ($i = 0; $i < 100; $i++) {
    $file->fwrite("Foo $i\n");
}

$file->seek(50);

echo json_encode(array(
    array('line' => $file->key(), 'contents' => trim($file->fgets())),
    array('line' => $file->key(), 'contents' => trim($file->fgets())),
    array('line' => $file->key(), 'contents' => trim($file->fgets())),
), JSON_PRETTY_PRINT);

?>

Results:

PHP  8.0.1+
[
    {
        "line": 50,
        "contents": "Foo 50"
    },
    {
        "line": 50,
        "contents": "Foo 51"
    },
    {
        "line": 51,
        "contents": "Foo 52"
    }
]

PHP 5.1 to 8.0.0
[
    {
        "line": 50,
        "contents": "Foo 51"
    },
    {
        "line": 51,
        "contents": "Foo 52"
    },
    {
        "line": 52,
        "contents": "Foo 53"
    }
]
Chris Johnson 22-Jan-2018 09:45
Note that this method will cause a PHP fatal error if the file being read contains no recognizable line termination characters and is larger than the allowable memory size for PHP to allocate, i.e. memory_limit set in php.ini or similar.  In other words, PHP keeps reading until it finds a line termination, if it runs out of memory first, it will throw a fatal error.

This is different from the file resource fread() function, which allows an optional maximum length argument to be passed to limit this behavior.
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