Using PHP is_bool() to Check Boolean Variables

In PHP programming, checking whether a variable is a boolean is often required; the language provides the built‑in is_bool() function for this purpose.

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

<?php
$var1 = true;
$var2 = false;
$var3 = 1;
$var4 = "true";

if (is_bool($var1)) {
    echo "变量 $var1 是布尔值<br>";
} else {
    echo "变量 $var1 不是布尔值<br>";
}
if (is_bool($var2)) {
    echo "变量 $var2 是布尔值<br>";
} else {
    echo "变量 $var2 不是布尔值<br>";
}
if (is_bool($var3)) {
    echo "变量 $var3 是布尔值<br>";
} else {
    echo "变量 $var3 不是布尔值<br>";
}
if (is_bool($var4)) {
    echo "变量 $var4 是布尔值<br>";
} else {
    echo "变量 $var4 不是布尔值<br>";
}
?>

The script defines four variables with different types—two booleans, an integer, and a string—and applies is_bool() to each, printing a message indicating whether the variable is a boolean.

变量 $var1 是布尔值
变量 $var2 是布尔值
变量 $var3 不是布尔值
变量 $var4 不是布尔值

From the output we see that only $var1 and $var2 are recognized as booleans because they were assigned the literal values true and false, while $var3 and $var4 are not.

Thus, is_bool() is a useful function for quickly determining a variable's boolean status, helping developers write more accurate and efficient PHP code.