How to Call JavaScript Function in PHP

In this article, we will introduce a method to call JavaScript function from PHP. We actually cannot call JavaScript function using PHP as these two languages do not understand each other. The only possible option is outputting the JavaScript function call in PHP. However, we also can write JavaScript in a PHP file and call the function.

Use the echo Function to Display the JavaScript Function Call in PHP

JavaScript is a client-side scripting language, while PHP is a server-side language. Technically, we cannot invoke JavaScript functions from PHP. But we can display the JavaScript using the echo function. This method includes the JavaScript function call in the output rather than the JavaScript function in PHP. We will define a JavaScript function first and then call the function. We can wrap the JavaScript invocation of the function with the echo function in PHP. Here, most work will be done by JavaScript, which is the function declaration and invocation. We will use PHP only to display the function invocation.

For example, create a PHP file index.php and inside the script tag write a JavaScript function showMessage(). Write the alert() function inside the showMessage() function. Write the text click here in the alert() function. Then, somewhere in the code, open the PHP tag and write the script tag and call the showMessage() function inside the tag. Then, wrap the script tag with the echo function.

We can also separate each element in the invocation by a single quote. The example is shown below.

echo '<script>', 'showMessage();', '</script>';

When we run the script, then an alert message will pop up saying click here. We treated the JavaScript function as a string and used it to display with the echo function. It should be noted that the function should be declared before the invocation. Thus, we called the JavaScript function in PHP using the echo function.

Example Code:

function showMessage() {
  alert('click here');
}

echo "<script> showMessage(); </script>";

Output:

click here