How to replace the first character with regular expression in php

In PHP, you can use the "preg_replace" function and the "/^./" regular expression to replace the first character. This function is used to perform a regular expression search and replacement. The syntax is " preg_replace('/^./', 'The first character after replacement', specified string)".

The operating environment of this tutorial: windows10 system, PHP7.1 version, DELL G3 computer

How to replace the first character with regular expression in php

The preg_replace function performs a regular expression search and replace.

Syntax

mixed preg_replace ( mixed $pattern , mixed $replacement , mixed $subject [, int $limit = -1 [, int &$count ]] )

Search for the part of subject that matches pattern and replace it with replacement.

Parameter description:

• $pattern: The pattern to be searched, which can be a string or a string array.

• $replacement: String or array of strings used for replacement.

• $subject: The target string or string array to be searched and replaced.

• $limit: Optional, the maximum number of substitutions for each subject string per pattern. The default is -1 (no limit).

• $count: Optional, the number of times the replacement is performed.

Return value

If subject is an array, preg_replace() returns an array, otherwise it returns a string.

If a match is found, the replaced subject is returned, otherwise the unchanged subject is returned. If an error occurs, NULL is returned.

The example is as follows:

<?php
$str = &#39;abcdefghi&#39;;
$str = preg_replace(&#39;/^./&#39;, &#39;A&#39;, $str);
echo $str;
?>

Output result:

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