PHP string function (5): delete or fill specified content

* 1.ltrim($str,$mask): Delete spaces or specified characters from the left

* 2.rtrim($str,$mask): Delete spaces or specified characters from the right

* 3.trim($str,$mask): Remove spaces or specified characters from the left and right edges

* 4.str_pad($str,$length,$mark,CONST): Use specific characters to Fill the string to the specified length

* You can use three constants to specify the direction: STR_PAD_LEFT/STR_PAD_RIGHT/STR_PAD_BOTH, and use spaces by default

* 5.chunk_split($str, $length,[$end ]): Cut the string into small pieces according to size, you can specify the delimiter

$str = '  php中文网   '; //左边二个空格,右边三个空格
$str1 = 'www.php.cn';
echo $str,&#39;<br>&#39;;
echo strlen($str),&#39;<br>&#39;;
echo &#39;<hr color="red">&#39;;

//1.ltrim($str,$mask): Remove spaces from the left or specify the character

echo ltrim($str),&#39;<br>&#39;;
echo strlen(ltrim($str)),&#39;<br>&#39;;
echo $str1,&#39;<br>&#39;;
echo strlen($str1),&#39;<br>&#39;;
echo ltrim($str1, &#39;www.&#39;),&#39;<br>&#39;;
echo strlen(ltrim($str1, &#39;www.&#39;)),&#39;<br>&#39;;

//2.rtrim($str,$mask): Delete spaces or specified characters from the right side

$str = '  php中文网   ';
echo rtrim($str),&#39;<br>&#39;;
echo strlen(rtrim($str)),&#39;<br>&#39;;

//3.trim($str,$mask): Delete spaces or specified characters from the left and right sides

$str = '  php中文网   ';
echo trim($str),&#39;<br>&#39;;
echo strlen(trim($str)),&#39;<br>&#39;;
echo &#39;<hr>&#39;;

//4.str_pad($str,$length,$mark,CONST): Use specific characters to pad the string to the specified length

$str1 = 'www.php.cn';
echo strlen($str1),&#39;<br>&#39;;
echo str_pad($str1, 20, &#39;*&#39;, STR_PAD_RIGHT),&#39;<br>&#39;; //默认向右填充
echo str_pad($str1, 20, &#39;*&#39;, STR_PAD_LEFT), &#39;<br>&#39;; //向左填充
echo str_pad($str1, 20, &#39;*&#39;, STR_PAD_BOTH), &#39;<br>&#39;; //二边填充
echo &#39;<hr>&#39;;

//5.chunk_split($str, $length,[$end]): Cut the string into small pieces according to size, you can specify the separator

$str1 = '12345678901234567890';
echo chunk_split($str1, 7, &#39;,&#39;),&#39;<br>&#39;;
echo chunk_split($str1, 7, &#39;<br>&#39;);