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Chapter 33. PHP and HTML

PHP and HTML interact a lot : PHP generate HTML, and HTML has informations that will be sent to PHP.

1. I'm trying to use an <input type="image"> tag, but the $foo.x and $foo.y variables aren't available. Where are they?
2. How do I create arrays in a HTML <form>?
3. How do I get all the results from a select multiple HTML tag?

1. I'm trying to use an <input type="image"> tag, but the $foo.x and $foo.y variables aren't available. Where are they?

When submitting a form, it is possible to use an image instead of the standard submit button with a tag like: 

<input type="image" src="image.gif" name="foo">
When the user clicks somewhere on the image, the accompanying form will be transmitted to the server with two additional variables: foo.x and foo.y.

Because $foo.x and $foo.y are invalid variable names in PHP, they are automagically converted to $foo_x and $foo_y. That is, the periods are replaced with underscores.

2. How do I create arrays in a HTML <form>?

To get your <form> result sent as an array to your PHP script you name the <input>, <select> or <textarea> elements like this: 

<input name="MyArray[]">
<input name="MyArray[]">
<input name="MyArray[]">
<input name="MyArray[]">
Notice the square brackets after the variable name, that's what makes it an array. You can group the elements into different arrays by assigning the same name to different elements: 

<input name="MyArray[]">
<input name="MyArray[]">
<input name="MyOtherArray[]">
<input name="MyOtherArray[]">
This produces two arrays, MyArray and MyOtherArray, that gets sent to the PHP script.

Note: You need not use indices with arrays in HTML, although you can specify number or associative indices, so you can exactly specify what indices will contain the information provided by that input element. If you do not specify indices, the array gets filled in the order the elements appear in the form.

For functions you can use to process these arrays once you get them into your scripts, please see the Arrays section.

3. How do I get all the results from a select multiple HTML tag?

The select multiple tag in an HTML construct allows users to select multiple items from a list. These items are then passed to the action handler for the form. The problem is that they are all passed with the same widget name. ie. 

<select name="var" multiple>
Each selected option will arrive at the action handler as: 

var=option1
var=option2
var=option3
Each option will overwrite the contents of the previous $var variable. The solution is to use PHP's "array from form element" feature. The following should be used: 

<select name="var[]" multiple>
This tells PHP to treat $var as an array and each assignment of a value to var[] adds an item to the array. The first item becomes $var[0], the next $var[1], etc. The count() function can be used to determine how many options were selected, and the sort() function can be used to sort the option array if necessary.

Note that if you are using JavaScript the [] on the element name might cause you problems when you try to refer to the element by name. Use it's numerical form element id instead, or enclose the variable name in single quotes and use that as the index to the elements array, for example: 

variable = documents.forms[0].elements['var[]'];

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