How do you write JavaScript code inside PHP?

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There are two main ways to write JavaScript code inside PHP:

1. Using the echo statement: You can use the echo statement to output any text or code, including JavaScript code. For example:

PHP

<?php
echo "<script>alert('Hello world!');</script>";
?>

This will generate the following HTML:

HTML

<script>alert('Hello world!');</script>

When the browser renders the HTML, it will execute the JavaScript code, which will display an alert message.

2. Using the heredoc syntax: The heredoc syntax allows you to create a string that spans multiple lines, without having to escape newline characters. This can be useful for writing JavaScript code, as it allows you to format the code in a way that is more readable and maintainable. For example:

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PHP

<?php
$script = <<<JS
$(function() {
  // JavaScript code goes here.
});
JS;

echo $script;
?>

This will generate the following HTML:

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HTML

<script>
$(function() {
  // JavaScript code goes here.
});
</script>

Which method you choose to use will depend on your personal preference. The echo the statement is simpler and more straightforward, but the heredoc syntax is more readable and maintainable.

Example

The following example shows how to use the heredoc syntax to write JavaScript code inside PHP:

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PHP

<?php
$script = <<<JS
$(function() {
  // Get the current time and display it in an alert message.
  var time = new Date();
  alert(time.toLocaleTimeString());
});
JS;

echo $script;
?>

When this code is executed, it will display an alert message with the current time.

Tips

• When writing JavaScript code inside PHP, be careful not to escape any special characters in the JavaScript code. For example, the double quote character (") is used to delimit strings in JavaScript, so you should not escape it in the PHP code.
• You can use PHP variables in your JavaScript code by embedding them in curly braces ({}). For example, the following code will display an alert message with the value of the PHP variable $name:

PHP

<?php
$name = "Bard";

echo <<<JS
$(function() {
  alert("Hello, {$name}!");
});
JS;
?>

• You can also use JavaScript functions to call PHP functions. To do this, you can use the ajax function in jQuery. For example, the following code will call the PHP function my_function() and display the result in an alert message:

PHP

<?php
function my_function() {
  return "Hello, world!";
}

echo <<<JS
$(function() {
  $.ajax({
    url: "my_script.php",
    type: "POST",
    data: {
      function: "my_function"
    },
    success: function(response) {
      alert(response);
    }
  });
});
JS;
?>

Conclusion

Writing JavaScript code inside PHP can be a useful way to add dynamic behaviour to your web pages. However, it is important to be careful not to escape any special characters in the JavaScript code, and to use PHP variables and JavaScript functions correctly.