How to convert uppercase letters to lowercase letters in php

Conversion method: 1. Use the "strtolower (string)" statement to convert the string to lowercase. 2. Use the "lcfirst(string)" statement to convert the first letter of the string to lowercase; 3. Use the "mb_strtolower(string, character encoding)" statement to convert the string to lowercase.

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

php converts uppercase letters to lowercase Letters

1) strtolower

strtolower() function can convert letters in a string to lowercase. The syntax format is as follows:

strtolower($string)

Among them, $string is a parameter of string type. This function can convert the parameter $string Convert the letters in to lowercase and return the converted string.

The sample code is as follows:

<?php
    $str = "HTTPS://WWW.PHP.CN/";
    $str = strtolower($str);
    echo $str;
?>

The running result is as follows:

//m.sbmmt.com/

2) lcfirst

lcfirst() function The first character of a string can be converted to lowercase. The syntax format is as follows:

lcfirst($str)

where $str is the string that needs to be converted.

The sample code is as follows:

<?php
    $str = &#39;Hello World!&#39;;
    $str = lcfirst($str);
    echo $str.&#39;<br>&#39;;
    $str2 = &#39;HELLO WORLD!&#39;;
    $str2 = lcfirst($str2);
    echo $str2;
?>

The running result is as follows:

hello World!
hELLO WORLD!

3) mb_strtolower

mb_strtolower The function of the () function is similar to the strtolower() function. It can also convert letters in the string to lowercase, and the mb_strtolower() function can also set the character encoding of the parameter. The syntax format is as follows:

mb_strtolower($str [, $encoding = mb_internal_encoding()])

Among them, $str is the string that needs to be converted, and $encoding is an optional parameter used to set the character encoding of the parameter.

The difference from the strtolower() function is that the detection of alphabetic characters in $str is based on the Unicode attribute of the character. The behavior of the function is therefore independent of the language setting and can convert any character with a "letter" attribute, such as the umlaut A (Ä).

The sample code is as follows:

<?php
    $str = "HTTP://WWW.PHP.CN/";
    $str = mb_strtolower($str);
    echo $str.&#39;<br>&#39;;
    $str = "Τάχιστη αλώπηξ βαφής ψημένη γη, δρασκελίζει υπέρ νωθρού κυνός";
    $str = mb_strtolower($str, &#39;UTF-8&#39;);
    echo $str;
?>

The running results are as follows:

//m.sbmmt.com/
τάχιστη αλώπηξ βαφής ψημένη γη, δρασκελίζει υπέρ νωθρού κυνός

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