PHP Strings

There might be many instances where you will create a program in PHP that takes a URL as input and does something with the address. This might be a site analysis or an image resize, but whatever the use is, you need to be sure that the URL will work or at least has the same format.

What users tend to leave out of a URL string is the http:// bit at the start. You could validate the URL to force the user to do this, but you will end up annoying a few people. By far the best way of making sure that the URL has the http:// bit at the start is by adding it behind the scenes. The best way to this is to remove the http:// from the start of the string, even if it isn't there and then add it back on.

I have talked before about truncating strings to include whole words, but what if you want to have complete sentences? The following function will truncate a string the number of words specified and until the sentence ends.

Using the strip_tags() function on any user generated input should be common practice in order to stop users putting in odd bits of HTML and messing up your nicely coded HTML. You might want to allow anchor tags to be used, which is fine, but some users might use this to include onmouseover and other events in order to run JavaScript annoyances on the page.

So after stripping all tags from your text you can then run the following function to turn any links into anchor elements. This will work with any plain text that you want to use it on.

Hiding your email address in an image is the best way of encrypting your email, but if your server doesn't support the GD2 library, or if you don't want to use it, then you might want to look at a different way of doing this.

The easiest way to encrypt your email address is to turn every character into the ASCII code equivalent and use this to display the text in HTML by putting a in front of each character. Here is a function that takes a string and turns it into HTML encoded text.

The reverse of turning ASCII text into HTML is to convert HTML into ASCII. And to this end here is a little function that does this.

Providing a text box for users to type information in is very common, but usually people want to include line breaks and links with the text and they expect the site to lay it out just as they had intended it. The following function will turn any ASCII text string into the approximate HTML equivalent.

Cutting a string to a specified length is accomplished with the substr() function. For example, the following string variable, which we will cut to a maximum of 30 characters.

The substr() function has three parameters. The first is the string, the second is where to start cutting from and the third is the amount of characters to cut to. So to cut to 30 characters we would use the following.

If you want to know the length of a string in PHP you would normally turn to the strlen() function which simply tells you the length of the string.

$string = 'this is a string';
$strLength = strlen($string);

To use this to check the length of the string use the following example.

The use of mod_rewrite on a site can have a powerful effect on search engine positioning, but to do it properly you will need to create a "slug" for each page. A slug is a lowercase alphanumeric version of the page title, with any spaces removed.

To get a slug you will need to use a function to turn a readable page title into a string that can be used as part of a URI.

This function is taken from Bramus and his excellent article about creating a post slug, and it does the job very nicely.

Use the following function to extract all of the links from a HTML string.