PHP Boolean data type false true usage introduction_PHP tutorial

In PHP, false and true means true and false. In PHP, it is called Boolean data type. It is a common data type for us. For example, conditional judgment is also a Boolean data type. Let’s introduce it to you below.

Grammar

To specify a Boolean value, use the keywords TRUE or FALSE. Both are not case sensitive.

The code is as follows

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代码如下	复制代码
$foo = True; // 赋值 TRUE to $foo ?>

$foo = True; // Assign TRUE to $foo ?>

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// == 真值判断语句 // equality and returns a boolean if ($action == "show_version") {     echo "The version is 1.0"; } // 这样写不是必须的... if ($show_separators == TRUE) {     echo " "; } // 直接写，更简单些 if ($show_separators) {     echo " "; }

Usually you use some operator to return a boolean value and pass it to the control flow.

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// == Truth value judgment statement

// equality and returns a boolean

if ($action == "show_version") {

代码如下	复制代码
$foo=false; $foo1=true; echo "为假时输出值为:".$foo; //没有输出值 echo " 为真时输出值为:".$foo1; //输出1

echo "The version is 1.0";

}

// It is not necessary to write this way...

if ($show_separators == TRUE) {

echo "

---

";
}

// Write directly, it’s easier
if ($show_separators) {
echo "

---

";
}

代码如下	复制代码
//$a=0; //$a=0.0; $a="0"; var_dump((bool) 0); echo " "; var_dump((bool) array()); if($a==false){ echo "空0默认转换为false，成功！"; }else{ echo "不能转换为false"; }

The Boolean type is the simplest type in PHP. Its value can be TRUE or FALSE. For example:

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$foo=false; $foo1=true; echo "When it is false, the output value is:".$foo; //No output value echo " When true, the output value is:".$foo1; //Output 1

Main details here: When converted to boolean, the following values ​​are considered FALSE: 1. the Boolean value FALSE itself 2. the integer value 0 (zero) 3. the floating point value 0.0 (zero), the empty string, and the string "0" 4. Array not including any elements 5. Objects that do not include any member variables (only applicable to PHP 4.0) 6. Special type NULL (including variables that have not been set) 7. SimpleXML objects generated from XML documents without any tags

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//$a=0; //$a=0.0; $a="0"; var_dump((bool) 0); echo " "; var_dump((bool) array()); if($a==false){ echo "Empty 0 is converted to false by default, success!"; }else{ echo "cannot be converted to false"; }

Output:

bool(false)
bool(false) Empty 0 is converted to false by default, success!

Convert to boolean
To explicitly convert a value to boolean, use (bool) or (boolean) to cast. But in many cases, casting is not necessary because when an operator, function, or flow control requires a boolean parameter, the value is automatically converted.

When converted to boolean, the following values ​​are considered FALSE:

Boolean value FALSE

Integer value 0 (zero)

Floating point value 0.0 (zero)

Blank string and string "0"

Array without member variables

Object without units (PHP 4 only)

Special type NULL (including variables that have not been set)

All other values ​​are considered TRUE (including any resources).

Conditional if else

if conditional statement syntax
The If construct is the most commonly used in programming languages. Its syntax is as follows:

if (expr)
statement
Among them, expr represents the condition, and statement represents the statement that should be executed after the condition is met. This means that if a certain condition (expr) is met, the following statement (statement) is executed. If the condition is not met, nothing is done.

An example is as follows:

After meeting the if condition, if the statement to be executed is more than one line, you need to surround the multi-line statement with braces {}. An example is as follows:

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代码如下	复制代码
$b)  echo "a is bigger than b";?>

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$ b) echo "a is bigger than b";?>

代码如下	复制代码
$b) {  echo "a is bigger than b";  $b = $a;}?>

The above example means that if the variable $a > $b , then output "a is bigger than b", otherwise, do nothing.

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$ b) { echo "a is bigger than b"; $b = $a;}?> What this example means is that if the variable $a > $b , then output "a is bigger than b" and assign $a to $b http://www.bkjia.com/PHPjc/628812.htmlwww.bkjia.com truehttp: //www.bkjia.com/PHPjc/628812.htmlTechArticleIn php, false true means true and false. In php, it is called Boolean data type. He is our A common data type, such as conditional judgment, is also a Boolean data type. Below we give...