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.

    错误／异常

    Throws a RuntimeException if the file cannot be read.

    示例

    示例 #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

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    用户贡献的备注 3 notes

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    5
    Lucas Bustamante
    3 years ago
    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"
    }
    ]
    up
    5
    Chris Johnson
    6 years ago
    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.
    up
    4
    Lucas Bustamante
    3 years ago
    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"
    }
    ]
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