What does php checked mean?

In PHP, checked is the attribute value of a check box, used to indicate whether a check box is checked.

Using the checked attribute, you can determine which check boxes are selected when processing form data so that you can process them accordingly.

In HTML, you can set the checked attribute to checked or empty to indicate whether the check box is checked. When the checked attribute is set to checked, it means that the check box is selected. When the checked attribute is empty, it means that the check box is not selected.

In PHP, submitted form data can be obtained through the $_POST or $_GET array. When a checkbox is selected, the corresponding key-value pair will be included in the array.

Here is a simple example that shows how to handle form data through the checked attribute:

<form method="post" action="submit.php">
  <input type="checkbox" name="option1" value="1" checked> Option 1 <br>
  <input type="checkbox" name="option2" value="2"> Option 2 <br>
  <input type="checkbox" name="option3" value="3" checked> Option 3 <br>
  <input type="submit" value="Submit">
</form>

In the above example, the first and third of the three checkboxes was preselected. When the user submits the form, the form data can be processed through the following code:

if(isset($_POST['option1'])) {
  // 处理选中 Option 1 的情况
}

if(isset($_POST['option2'])) {
  // 处理选中 Option 2 的情况
}

if(isset($_POST['option3'])) {
  // 处理选中 Option 3 的情况
}

The above code uses the isset function to determine whether the option is selected.

In short, checked is a very useful attribute for handling the checked state of the check box. In PHP, by obtaining the submitted form data, you can perform corresponding processing based on the selected status of the check box.

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