Several commonly used PHP string functions

<?PHP$a= "@[email protected]"; $trim=Trim($a,‘@‘);//Remove the @//var_dump ($trim) on the left and right side;    $ltrim=LTrim($a,‘@‘);//Remove the @//var_dump ($ltrim) on the left;    $rtrim=RTrim($a,‘@‘);//Remove the @//var_dump ($rtrim) on the right;    $strlen=strlen($a);//the length of the statistic string//var_dump ($strlen);    $strrev=Strrev($a);//Invert string//var_dump ($strrev);    $str _shuffle=Str_shuffle($a);//randomly scrambled string//var_dump ($str _shuffle);    $explode=Explode(' A ',$a);//a split string is an array of//var_dump ($explode);    $implode=implode(' A ',$explode);//put $explode this array using a stitching for string//var_dump ($implode);    $str _replace=Str_replace(' A ', ' B ',$a);//string substitution replaces a in a $ A string with B//var_dump ($str _replace);    $strpos=Strpos($a, ' Q ');//find the position where Q first appeared in $ A//var_dump ($strpos);    $strrpos=Strrpos($a, ' Q ');//find the last position of Q in $ A//var_dump ($strrpos);    $b= ' I love You '; $strtoupper=Strtoupper($b);//the string is converted to uppercase//var_dump ($strtoupper);    $c= ' I Love You '; $strtolower=Strtolower($c);//the string is converted to lowercase//var_dump ($strtolower);    $ucwords=Ucwords($b);//the first letter of each word in the string is capitalized//var_dump ($ucwords);    $ucfirst=Ucfirst($b);//write//var_dump of the first letter of the string ($ucfirst);    $substr=substr($a, '-1 ');//string interception starts from the countdown to the first intercept of//var_dump ($SUBSTR);    $strstr=strstr($a, ' Q ');//finds the position where Q first appears in the string $ A and returns the position to the end of the string//var_dump ($STRSTR);    $STRRCHR=STRRCHR($a, ' Q ');//Find Q Returns the string from this position to the end at the last occurrence of the string//var_dump ($STRRCHR);    $str _repeat=str_repeat($a, ' 2 ');//repeat $ A of this string 2 times after the result//var_dump ($str _repeat);?>

Several commonly used PHP string functions