Clearing up php retrieval of form variables
the basics on how to best submit and retrieve form values in php focusing on checkboxes because they seem to be the most diffucult to understand.
When posting form data to another page your naming convention makes all the difference in the world in your ease of access and clarity.
Your Options
simple syntax name="simple_syntax"
array syntax name="array_syntax[]"
multi-dimensional arrays name="multi-dimensional_array_syntax[][]"
simple syntax
<form name="av" method="post" action="<?php print $_SERVER['PHP_SELF']; ?>">
<p>Simple checkbox <input type="checkbox" name="simple_checkbox_1" value="simple_checkbox_1"/>
<input type="checkbox" name="simple_checkbox_2" value="simple_checkbox_2"/>
<input type="checkbox" name="simple_checkbox_3" value="simple_checkbox_3"/></p>
</form>
assuming each checkbox was checked your $_POST should now look like this
$_POST => array (
[simple_checkbox_1] => simple_checkbox_1
[simple_checkbox_2] => simple_checkbox_2
[simple_checkbox_3] => simple_checkbox_3
)
any checkbox unchecked would simply not show in the results: so if checkbox 2 was not checked you $_POST would be
$_POST => array (
[simple_checkbox_1] => simple_checkbox_1
[simple_checkbox_3] => simple_checkbox_3
)
note: this only applies to checkboxes: if we had used text inputs the result would be
$_POST => array (
[text_1] => text_1
[text_2] =>
[text_3] => text_3
)
array syntax
<form name="av" method="post" action="<?php print $_SERVER['PHP_SELF']; ?>">
<p>Simple array checkbox <input type="checkbox" name="simple_array_checkbox[]" value="simple_array_checkbox_1"/>
<input type="checkbox" name="simple_array_checkbox[]" value="simple_array_checkbox_2"/>
<input type="checkbox" name="simple_array_checkbox[]" value="simple_array_checkbox_3"/></p>
</form>
assuming each checkbox was checked your $_POST should now look like this
$_POST => array (
[simple_array_checkbox] => Array
(
[0] => simple_array_checkbox_1
[1] => simple_array_checkbox_2
[2] => simple_array_checkbox_3
)
)
leaving one unchecked will make that value dissapear from the array
$_POST => array (
[simple_array_checkbox] => Array
(
[0] => simple_array_checkbox_1
[1] => simple_array_checkbox_3
)
)
notice that our array index does not skip a number for the unchecked checkbox
note: repeating form names without using array syntax will just overwrite any previous value
<form name="av" method="post" action="<?php print $_SERVER['PHP_SELF']; ?>">
<input type="checkbox" name="array_checkbox" value="array_checkbox_1"/>
<input type="checkbox" name="array_checkbox" value="array_checkbox_2"/></p>
</form>
will result in
$_POST => array (
[array_checkbox] => array_checkbox_2
)
indexed array syntax
<form name="av" method="post" action="<?php print $_SERVER['PHP_SELF']; ?>">
<p>Indexed array checkbox <input type="checkbox" name="indexed_array_checkbox[0]" value="indexed_array_checkbox_1"/>
<input type="checkbox" name="indexed_array_checkbox[1]" value="indexed_array_checkbox_2"/>
<input type="checkbox" name="indexed_array_checkbox[2]" value="indexed_array_checkbox_3"/></p>
</form>
assuming each checkbox was checked your $_POST should now look like this
$_POST => array (
[indexed_array_checkbox] => Array
(
[0] => indexed_array_checkbox_1
[1] => indexed_array_checkbox_2
[2] => indexed_array_checkbox_3
)
)
leaving one unchecked will make that value dissapear from the array
$_POST => array (
[simple_array_checkbox] => Array
(
[0] => indexed_array_checkbox_1
[2] => indexed_array_checkbox_3
)
)
notice that our array index is maintained even with an unchecked checkbox
multi-dimensional array checkbox
<form name="av" method="post" action="<?php print $_SERVER['PHP_SELF']; ?>">
<p>Multi-dimensional array checkbox <br/>
Row 1 <input type="checkbox" name="complex_array_checkbox[row_1][]" value="complex_array_checkbox_row_1_1"/>
<input type="checkbox" name="complex_array_checkbox[row_1][]" value="complex_array_checkbox_row_1_2"/>
<input type="checkbox" name="complex_array_checkbox[row_1][]" value="complex_array_checkbox_row_1_3"/><br/>
Row 2 <input type="checkbox" name="complex_array_checkbox[row_2][]" value="complex_array_checkbox_row_2_1"/>
<input type="checkbox" name="complex_array_checkbox[row_2][]" value="complex_array_checkbox_row_2_2"/>
<input type="checkbox" name="complex_array_checkbox[row_2][]" value="complex_array_checkbox_row_2_3"/><br/>
Row 3 <input type="checkbox" name="complex_array_checkbox[row_3][]" value="complex_array_checkbox_row_3_1"/>
<input type="checkbox" name="complex_array_checkbox[row_3][]" value="complex_array_checkbox_row_3_2"/>
<input type="checkbox" name="complex_array_checkbox[row_3][]" value="complex_array_checkbox_row_3_3"/></p>
</form>
assuming each checkbox was checked your $_POST should now look like this
$_POST => array (
[complex_array_checkbox] => Array
(
[row_1] => Array
(
[0] => complex_array_checkbox_row_1_1
[1] => complex_array_checkbox_row_1_2
[2] => complex_array_checkbox_row_1_3
)
[row_2] => Array
(
[0] => complex_array_checkbox_row_2_1
[1] => complex_array_checkbox_row_2_2
[2] => complex_array_checkbox_row_2_3
)
[row_3] => Array
(
[0] => complex_array_checkbox_row_3_1
[1] => complex_array_checkbox_row_3_2
[2] => complex_array_checkbox_row_3_3
)
)
)
leaving some unchecked will make those values dissapear from the array
$_POST => array (
[complex_array_checkbox] => Array
(
[row_1] => Array
(
[0] => complex_array_checkbox_row_1_2
[1] => complex_array_checkbox_row_1_3
)
[row_2] => Array
(
[0] => complex_array_checkbox_row_2_1
[1] => complex_array_checkbox_row_2_3
)
)
)
a fully unindexed multi-dimensional array checkbox is not very helpful using the same form your $_POST would be
$_POST => array (
[complex_array_checkbox] => Array
(
[0] => Array
(
[0] => complex_array_checkbox_row_1_1
)
[1] => Array
(
[0] => complex_array_checkbox_row_1_2
)
[2] => Array
(
[0] => complex_array_checkbox_row_1_3
)
[3] => Array
(
[0] => complex_array_checkbox_row_2_1
)
[4] => Array
(
[0] => complex_array_checkbox_row_2_2
)
[5] => Array
(
[0] => complex_array_checkbox_row_2_3
)
[6] => Array
(
[0] => complex_array_checkbox_row_3_1
)
[7] => Array
(
[0] => complex_array_checkbox_row_3_2
)
[8] => Array
(
[0] => complex_array_checkbox_row_3_3
)
)
)
