How to dynamically set the readOnly property of input through PHP code?

PHP dynamically sets the readOnly property of the input element

In web development, it is often necessary to dynamically control the read-only attributes of the input element according to different conditions. This article will introduce how to effectively implement this feature using PHP and correct some common misunderstandings.

Many developers try to use methods like readonly="true" or readonly="false" , but in fact, the setting of readonly property is not controlled by a boolean value. As long as the readonly attribute exists, the input element will be in a read-only state regardless of its value.

Here is a correct PHP code example that dynamically sets readonly property based on the existence or absence of the $_GET['username'] variable:

<input type="text" name="username" value="<?php echo isset($_GET['username']) ? $_GET['username'] : ''; ?>" echo isset :>>

The core of this code lies in <?php echo isset($_GET[&#39;username&#39;]) ? &#39;readonly&#39; : &#39;&#39;; ?> part. If $_GET['username'] exists, the readonly attribute is output, making the input element read-only; otherwise, no attributes are output, and the input element remains editable.

This method avoids the use of JavaScript, and directly completes the dynamic control of readonly attributes through PHP code on the server side, improving code efficiency and readability. The expected functions are achieved without complex JavaScript operations.

Therefore, the correct way is to determine whether to add the readonly property itself based on the condition, rather than trying to control its state by setting its value to true or false .

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