How to use php fseek function?

php The fseek function is used to locate in an open file. Its syntax is fseek(file,offset,whence). The parameter file is required and refers to specifying the file to be located; offset is required and refers to specifying the new position (from The beginning of the file header is measured in bytes).

#php How to use fseek function?

Definition and Usage

The fseek() function locates in an open file.

This function moves the file pointer forward or backward from the current position to a new position, measured in bytes from the beginning of the file.

Returns 0 if successful; otherwise returns -1. Note that moving to a position after EOF does not produce an error.

Syntax

fseek(file,offset,whence)

Parameters

file Required. Specifies the file to locate in.

offset Required. Specifies the new position (measured in bytes from the beginning of the file).

whence Optional. Possible values:

SEEK_SET - Set position equal to offset bytes. default.

SEEK_CUR - Set the position to the current position plus offset.

SEEK_END - Set the position to the end of the file plus offset (to move to the position before the end of the file, offset must be a negative value).

Explanation

whence parameter was added after PHP 4.0.0.

Tips and Notes

Tip: Find the current position by using ftell().

Example

<?php
$file = fopen("test.txt","r");
// 读取第一行
fgets($file);
// 倒回文件的开头
fseek($file,0);
?>

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