SymfonyWorld Online 2022 Winter Edition

SplFileObject::fgets

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

SplFileObject::fgetsファイルから 1 行取り出す

説明

public SplFileObject::fgets(): string

ファイルから 1 行取り出します。

パラメータ

この関数にはパラメータはありません。

戻り値

ファイルから次の行を含む文字列、もしくはエラーのときは false を返します。

エラー / 例外

ファイルが読み込みできない場合 RuntimeException がスローされます。

例1 SplFileObject::fgets() の例

この例では file.txt の内容が 1 行ごとに出力されます。

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

参考

add a note

User Contributed Notes 3 notes

up
4
Chris Johnson
4 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
1
Lucas Bustamante
8 months 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"
    }
]
up
1
Lucas Bustamante
8 months 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"
    }
]
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