PHP boolean data type false true usage Introduction

In php, false true indicates true or false. in php, it is called a boolean data type. It is a common data type. For example, conditional judgment is also a boolean data type, the following is an introduction.

Syntax

To specify a Boolean value, use the keyword TRUE or FALSE. Both are case insensitive.

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<? Php $ Foo = True; // value TRUE to $ foo ?>

You usually use some operators to return a boolean value and pass it to the control process.

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// = True value judgment statement // Equality and returns a boolean If ($ action = "show_version "){ Echo "The version is 1.0 "; } // This write is not required... If ($ show_separators = TRUE ){ Echo "} // Write directly, which is simpler If ($ show_separators ){ Echo "}

Boolean is the simplest type in PHP. The value can be TRUE or FALSE.

For example:

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$ Foo = false; $ Foo1 = true; When echo "is false, the output value is:". $ foo; // No output value Echo "<br/> true:". $ foo1; // output 1

The main details are as follows:

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

1. the Boolean value is FALSE.
2. the integer value is 0 (0)
3. the floating point value is a 0.0 (zero) null string and the string "0"
4. arrays that do not contain any elements
5. objects that do not include any member variables (applicable only to PHP 4.0)
6. Special Type NULL (including unset variables)
7. SimpleXML object generated from XML documents without any tags

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// $ A = 0; // $ A = 0.0; $ A = "0 "; Var_dump (bool) 0 ); Echo "<br/> "; Var_dump (bool) array ()); If ($ a = false ){ Echo "null 0 is converted to false by default. Success! "; } Else { Echo "cannot be converted to false "; }

Output:

Bool (false)
Bool (false) null 0 is converted to false by default. Success!

Convert to a Boolean Value
To convert a value to a boolean value explicitly, use (bool) or (boolean) to forcibly convert the value. However, in many cases, forced conversion is not required, because this value is automatically converted when an operator, function, or flow control requires a boolean parameter.

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

Boolean value FALSE

Integer value 0 (0)

Floating point value: 0.0 (0)

Blank string and string "0"

Array without member variables

Objects without cells (applicable only to PHP 4)

Special Type NULL (including unset variables)

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

Condition if else

If Condition Statement syntax
The If structure is the most commonly used in programming languages. The syntax is as follows:

If (expr)
Statement
Expr indicates the condition, and statement indicates the statement to be executed after the condition is met. This means that if a condition (expr) is met, the following statement (statement) will be executed. If the condition is not met, nothing will be done.

Example:

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<? Phpif ($ a> $ B) echo "a is bigger than B";?>

The preceding example indicates that if the variable $ a> $ B, "a is bigger than B" is output. Otherwise, nothing is done.

After the if condition is met, if the statement to be executed has more than one row, enclose the multi-row statement with braces. Example:

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<? Phpif ($ a> $ B) {echo "a is bigger than B"; $ B = $ a ;}?>

In this example, if the variable $ a> $ B, output "a is bigger than B" and assign $ a to $ B.