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When performing the duties of creating/manipulating web content, the PHP programmer will need to modify the lengths of strings, either by padding the strings to be a certain length or removing strings to be a certain length. PHP provides numerous built-in functions to accomplish these tasks. The following are the most common functions for modifying string lengths: • ltrim -          The name of this function identifies its purpose, to trim the string content starting from the left portion of the string. By default, the ltrim() function will remove all white space characters which includes the standard space, the horizontal tab(\t), vertical tab (\x0b), new line (\n), carriage return (\r) and NULL (\0). This function will continue to remove these characters until it reaches a non-white space character and then the function removal process will terminate. <?php $text = \n\t Jane wanted to listen to the troupe play."; print ltrim($text); // The new text printed wi

• array_flip -                     This function is the opposite function for the get_html_translation_table() function by reversing HTML special characters back their original string characters. <?php $html_text = "J&uacute;an and Fel&iacute;pe paid 13&cent; a piece for gum." $translation_table = get_html_translation_table(HTML_ENTITIES); $flipped = array_flip($translation_table); print strtr($html_text, $flipped); // The sentence will now read "Júan and Felípe paid 13¢ a piece for // gum" without any HTML translation ?> • strip_tags () -                        This function removes all HTML and PHP tags from a string. <?php $html_text = "<a href=\"http://www.johnsgifts.com\"><strong> John's Gifts</strong></a>"; print strip_tags($html_text); // Returns John's Gifts with no HTML tags ?> In the even that a tag type should remain while all others are removed, that

PHP's strength is in its ability to turn a static web page into a dynamic web page by interacting directly with the HTML. Part of this strength is PHP's ability to convert non-HTML (text only) strings to HTML and HTML strings to non-HTML strings. To make this happen, PHP provides multiple built-in functions designed specifically for HTML conversions. The following is a list of the most commonly used: Text to HTML Conversion Functions • nl2br -             This function name (nl2br) is an acronym for "newline to <br /> tags" due to the fact that this function will convert all newline characters (\n) in strings to their XHTML-compliant equivalent (<br />). <?php $text = "See Spot. See Spot run. See Spot fall. See Spot's friends laugh. Hear Spot growl. See Spot's friends run."; print nl2br($text); // The sentence will now read "See Spot.<br />See Spot run. // <br />See Spot fall.<br />See Spo

Case sensitivity is an issue that the programmer (and the end user) must deal with. Everything from commands to passwords are affected by case sensitivity. In PHP there are four functions that provide the tools to deal with the case sensitivity issue by allowing the string case to be manipulated. • strtolower -                  This string case manipulation function converts all characters that are uppercase characters to lowercase characters. <?php $text = "MySQL http://WWW.MYSQL.COM"; print strtolower($text); // Returns "mysql http://www.mysql.com"; ?> • strtoupper -  This string case manipulation function converts all characters that are lowercase characters to uppercase characters. <?php $text = "MySQL http://WWW.MYSQL.COM"; print strtoupper($text); // Returns "MYSQL HTTP://WWW.MYSQL.COM"; ?> • ucfirst -                   This string case manipulation function converts only the first character of the

While the strcmp() function is the most commonly used string comparison function in PHP, there are other string comparison functions offered: • strcasecmp -                This string comparison function is equivalent to the strcmp() function except that it is not case sensitive. <?php function chk_emails($input1, $input2) { if (! strcasecomp($input1, $input2)) { print "E-mails are the same, proceed<br>"; }else { print "E-mails are not equal<br>"; } } chk_emails("jones@mysql.com","Jones@MySQL.com"); // strcasecmp is case-insensitive and thus these two e-mails // are the same ?> • strspn -               The strspn() function compares two strings to determine how closely related they are to each other. This is accomplished by returning the length of the first string containing characters that are also located in the second string. <?php function passwd_diff($n_passwd, $o_passwd) { if (strspn($n_p

Following the password example just shown, there are many web sites today that force a person to type there password in twice to make sure that they truly are setting it to what they want (the chances of typing it identically wrong twice is very low). This is accomplished using such tools as strcmp() which is a built-in to PHP. <?php Function chk_passwds($input1, $input2) { if (strcomp($input1, $input2) = 0) { print "Passwords are equal, proceed<br>"; }else { print "Passwords are not equal<br>"; } } chk_passwds("doggy1", "Doggy1"); // strcmp is case-sensitive and thus these passwords are not equal ?> The strcomp() function has three possible results: 0 means the two strings are equal, -1 means that the first string is less than the second string and 1 means that the second string is less than the first string. In the example above, all that needs to be tested is if they are equal. It is not necessary to kno

As stated, PHP has poweful regular expressions that provide programmers with the tools necessary to complete difficult searching tasks. In addition to this regular expression capability, PHP provides built-in functionality for performing a wide range of string-specific tasks. Many of these tasks are based on string comparison operations. String Length One of the simplest comparison operators of strings is determining if the lengths are equivalent. This involves determining the length of the strings and then acting upon those lengths. The length function built-in to PHP is strlen() and is one of the more widely used string expressions. <?php function chk_passwd($input) { if (strlen($input) < 7) { print "Password is too short"; } else if (strlen($input) > 10) { print "Password is too long"; }else { print "Password is the proper length, proceed<br>"; } } chk_passwd("doggy1"); chk_passwd("Diabolical");