Count array key that contain specific string
<p>I have an array like that contain key with same name but with number at the end</p>

<p>array example:</p>

<pre><code>Array
(
    [field_name0] =&gt; name 
    [field_name1] =&gt; sku_package_height 
    [field_name2] =&gt; sku_package_width
    [custom_field] =&gt; 13
    [attribute] =&gt; 'test'
    [field_name3] =&gt; sku_package_length 
    [field_name4] =&gt; sku_package_weight
)
</code></pre>

<p>from the example above i want to count how many record that has array key that contain <code>field_name</code>, so the result I want will be <code>5</code></p>