PHP 大小写转换、首字母大写、每个单词首字母大写转换相关函数

1.strtolower(): 该函数将传入的字符串参数所有的字符都转换成小写,并以小定形式放回这个字符串.

    <?php 
    $str = "Mary Had A Little Lamb and She LOVED It So"; 
    $str = strtolower($str); 
    echo $str; // Prints mary had a little lamb and she loved it so 
    ?>  

2.strtoupper(): 该函数的作用同strtolower函数相反,是将传入的字符参数的字符全部转换成大写,并以大写的形式返回这个字符串.用法同strtolowe()一样.

    <?php 
    $str = "Mary Had A Little Lamb and She LOVED It So"; 
    $str = strtoupper($str); 
    echo $str; // Prints MARY HAD A LITTLE LAMB AND SHE LOVED IT SO 
    ?>  

3.ucfirst(): 该函数的作用是将字符串的第一个字符改成大写,该函数返回首字符大写的字符串.用法同strtolowe()一样.

    <?php 
    $foo = "hello world!"; 
    $foo = ucfirst($foo);             // Hello world! 
     
    $bar = "HELLO WORLD!"; 
    $bar = ucfirst($bar);             // HELLO WORLD! 
    $bar = ucfirst(strtolower($bar)); // Hello world! 
    ?>  

4.ucwords()：该函数将传入的字符串的每个单词的首字符变成大写。如"imphper cn"，经过该函数处理后，将返回"Imphper Cn"。用法同strtolower()一样。

    <?php 
    $foo = "hello world!"; 
    $foo = ucwords($foo);             // Hello World!  
     
    $bar = "HELLO WORLD!"; 
    $bar = ucwords($bar);             // HELLO WORLD! 
    $bar = ucwords(strtolower($bar)); // Hello World! 
    ?>