You want to know if an array contains a certain key.
Use array_key_exists() to check for a key no matter what the associated value is. This fnction ignores array values. It just reports whether there is an element in the array with a particular key.
Use isset() to find a key whose associated value is anything but null. A null value causes the funtion to return false.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="EN" lang="EN">
<head>
<title>PHP</title>
<meta Name="Author" Content="Hann So">
</head>
<body>
<p>
<?php
$fruits = array('red'=>'Apples', 'green'=>'Grapes', 'yellow'=>'Bananas', 'orange'=>'Oranges');
print_r($fruits);
echo "<p><b>Use array_key_exists() to check.</b></p>";
if (array_key_exists('green', $fruits)) {
echo "The value for green key is ", $fruits['green'], ".<br />";
}
else {
echo "There's no green key.<br />";
}
if (array_key_exists('black', $fruits)) {
echo "The value for green key is ", $fruits['black'], ".<br />";
}
else {
echo "There's no black key.<br />";
}
echo "<p><b>Use array_key_exists() to check.</b></p>";
if (isset($fruits['green'])) {
echo "The value for green key is ", $fruits['green'], ".<br />";
}
else {
echo "There's no green key.<br />";
}
if (isset($fruits['black'])) {
echo "The value for gree key is ", $fruits['black'], ".<br />";
}
else {
echo "There's no black key.<br />";
}
?>
</p>
</body>
</html>
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