Characters, they make up the gist of what we see on the internet. Whether they are of the alphanumeric, numeric or printable variety, it's certainly helpful to have a function within PHP that allows for the ability to manipulate and return them according to our particular desires.

There are several functions that make up the PHP 'character' series, but I will cover 7 of them today. I use most of these regularly, whenever situations call for them.

For this function, we use the 'ctype' clause, where each particular function name is appended after it with an underscore in-between.

Alphanumeric Characters - ctype_alnum

<?php $examples = array('1890ABCD', 'DCBA0981#'); foreach ($examples as $example) { if (ctype_alnum($example)) { echo "<div class="samples">"; echo "$example contains only letters and digits. n"; echo "</div>"; } else { echo "<div class="samples">"; echo "$example does not contain only letters and digits. n"; echo "</div>"; } } ?>
The result of the above code block will be...


This would make sense, as the '#' is not alphanumeric. As you can see, this is self-explanatory function. Using arrays is a good idea when searching for particular characters, as is creating conditions for getting particular returns. I use both in all the examples below.

Alpha Characters - ctype_alpha

This function will return letters.

<?php $examples = array('ABCDefgh', 'DCBA0981'); foreach ($examples as $example) { if (ctype_alpha($example)) { echo "<div class="samples">"; echo "$example contains only letters. n"; echo "</div>"; } else { echo "<div class="samples">"; echo "$example does not contain only letters. n"; echo "</div>"; } } ?>
The result...

Control Characters - ctype_cntrl

This function will return control characters if they are found within the array. That won't happen very often, as most characters returned on a web page in a browser are printable and don't offer much in the way of control. This function could be used more for content management systems, as opposed to the creation of website pages.

<?php $examples = array('U+0000', 'carriagen'); foreach ($examples as $example) { if (ctype_cntrl($example)) { echo "<div class="samples">"; echo "$example contains control characters. n"; echo "</div>"; } else { echo "<div class="samples">"; echo "$example does not contain control characters. n"; echo "</div>"; } } ?>
The result...

Digit Characters - ctype_digit

Returns strings which contain digits. Take note that this function does not recognize decimals.

<?php $examples = array('10800', '10800.67'); foreach ($examples as $example) { if (ctype_digit($example)) { echo "<div class="samples">"; echo "$example contains all digits. n"; echo "</div>"; } else { echo "<div class="samples">"; echo "$example does not contain all digits. n"; echo "</div>"; } } ?>
The result...

Printable Characters - ctype_print

It's great to be able to locate printable characters. This function can be used for safety measures, as well as making for a better user experience for visitors to a website. 'ctype_graph' can also be used, however, 'print' recognizes whitespace as being printable. Thus, making it easier to use.

<?php $examples = array('^7Up#', 'I am printable.'); foreach ($examples as $example) { if (ctype_print($example)) { echo "<div class="samples">"; echo "$example contains visible printable characters. n"; echo "</div>"; } else { echo "<div class="samples">"; echo "$example does not contain visible printable characters. n"; echo "</div>"; } } ?>
The result...

Lowercase Characters - ctype_lower

Find lowercase characters and return accordingly.

<?php $examples = array('UPPERCASE', 'lowercase'); foreach ($examples as $example) { if (ctype_lower($example)) { echo "<div class="samples">"; echo "$example contains all lower case letters. n"; echo "</div>"; } else { echo "<div class="samples">"; echo "$example does not contain lower case letters. n"; echo "</div>"; } } ?>
The result...

Uppercase Characters - ctype_upper

Find uppercase characters and return accordingly.

<?php $examples = array('UPPERCASE', 'lowercase'); foreach ($examples as $example) { if (ctype_upper($example)) { echo "<div class="samples">"; echo "$example contains all upper case letters. n"; echo "</div>"; } else { echo "<div class="samples">"; echo "$example does not contain upper case letters. n"; echo "</div>"; } } ?>
The result...


As you can probably see, these examples could be taken to much higher levels. While and for loops could be used, as well as more in-depth conditional statements, providing much in the way of furthering better experiences for both back and front end users. I highly suggest you do more research on the PHP 'character' function and see what you can come up with.