Using PHP’s is_bool() Function to Check Boolean Variables

In PHP programming, checking whether a variable holds a boolean value is a common task, and the language provides the built‑in is_bool() function for this purpose.

The is_bool() function returns true if the supplied variable is of type boolean and false otherwise.

Below is a complete example that defines four variables with different types and uses is_bool() to test each one:

<code style="font-family: 'Operator Mono', Consolas, Monaco, Menlo, monospace; font-size: 12px; display: -webkit-box; padding: 15px 16px 16px; color: rgb(171, 178, 191)"><?php<br/>$var1 = true;<br/>$var2 = false;<br/>$var3 = 1;<br/>$var4 = "true";<br/><br/>if (is_bool($var1)) {<br/>    echo "变量 $var1 是布尔值<br>";<br/>} else {<br/>    echo "变量 $var1 不是布尔值<br>";<br/>}<br/><br/>if (is_bool($var2)) {<br/>    echo "变量 $var2 是布尔值<br>";<br/>} else {<br/>    echo "变量 $var2 不是布尔值<br>";<br/>}<br/><br/>if (is_bool($var3)) {<br/>    echo "变量 $var3 是布尔值<br>";<br/>} else {<br/>    echo "变量 $var3 不是布尔值<br>";<br/>}<br/><br/>if (is_bool($var4)) {<br/>    echo "变量 $var4 是布尔值<br>";<br/>} else {<br/>    echo "变量 $var4 不是布尔值<br>";<br/>}<br/>?></code>

Running this script produces the following output, indicating which variables are recognized as booleans:

<code style="font-family: 'Operator Mono', Consolas, Monaco, Menlo, monospace; font-size: 12px; display: -webkit-box; padding: 15px 16px 16px; color: rgb(171, 178, 191)">变量 $var1 是布尔值<br/>变量 $var2 是布尔值<br/>变量 $var3 不是布尔值<br/>变量 $var4 不是布尔值<br/></code>

The result shows that $var1 and $var2 are boolean values because they were assigned the literals true and false. In contrast, $var3 holds an integer (1) and $var4 holds a string ("true"), so is_bool() correctly reports them as non‑boolean.

In summary, the is_bool() function is a simple yet powerful tool for quickly determining a variable’s boolean status, which is essential for reliable type checking in PHP applications.