What does this !== mean in php and is there any doc's on it?
PHP comparison operators, "Not identical" (5th in the table)
This operator works much like != but also checks the type of the operands. For example:
3 != '3' is false, but 3 !== '3' is true.
== is the comparison operator you're familiar with: if two values are equivalent, they == each other. There's some type coercion that goes on before the comparison.
4 == '4' // true: equivalent value, different type
=== is a more strict comparison that requires that values be of the same type.
4 === 4 // true: same value, same type
'4' === '4' // true: same value, same type
4 === '4' // false: equivalent value, different type
!== is the opposite of the strict comparison operator, so it is true when two values are of a different type or different value or both.
4 !== 3 // true: different value, same type
4 !== '4' // true: equivalent value, different type
'4' !== 3 // true: different value, different type
'4' !== '3' // true: different value, same type
4 !== 4 // false: same value, same type
It means "not equal or not the same type".
This shows the difference between != and !==:
"5"!=5 //returns false
"5"!==5 //returns true
That is the not identical operator
$a !== $b
Returns TRUE if $a is not equal to $b, or they are not of the same type.
For example, it is used to check if a variable is false and not 0, since 0 is the same that false for PHP.
$bar = 0;
if ($bar != false) { echo '$bar != false'; } // won't output the text
if ($bar !== false) { echo '$bar !== false'; } // will output the text
!= is used for value only
but
!== is used for value and type both
suppose:
$a = "5"; // String
$b = 5; // Integer
$a!=$b // false
$a!==$b // true
That's the difference.
Related
<?php
$test = "-3,-13";
if ($test == -3) {
echo "yay";
} else {
echo "nay";
}
?>
why it always runs through if condition and not going in else condition? I am new to php so do not know what's going on here.
The string is converted into an integer "-3, 46, blala" -> -3 , then the condition is evaluated.
Use the === operator to avoid conversion.
Most of the time, you do not want to let php do the conversion in your place (security problem). Rather, the request is refused.
As PHP documentation says
Example Name Result
$a == $b Equal TRUE if $a is equal to $b after type juggling.
$a === $b Identical TRUE if $a is equal to $b, and they are of the same type.
When we compare a number with a string, the string is converted to a number and the comparison performed numerically.
var_dump(0 == "a"); // 0 == 0 -> true
var_dump("1" == "01"); // 1 == 1 -> true
https://www.php.net/manual/en/language.operators.comparison.php
I've always done this: if ($foo !== $bar)
But I realized that if ($foo != $bar) is correct too.
Double = still works and has always worked for me, but whenever I search PHP operators I find no information on double =, so I assume I've always have done this wrong, but it works anyway. Should I change all my !== to != just for the sake of it?
== and != do not take into account the data type of the variables you compare. So these would all return true:
'0' == 0
false == 0
NULL == false
=== and !== do take into account the data type. That means comparing a string to a boolean will never be true because they're of different types for example. These will all return false:
'0' === 0
false === 0
NULL === false
You should compare data types for functions that return values that could possibly be of ambiguous truthy/falsy value. A well-known example is strpos():
// This returns 0 because F exists as the first character, but as my above example,
// 0 could mean false, so using == or != would return an incorrect result
var_dump(strpos('Foo', 'F') != false); // bool(false)
var_dump(strpos('Foo', 'F') !== false); // bool(true), it exists so false isn't returned
!== should match the value and data type
!= just match the value ignoring the data type
$num = '1';
$num2 = 1;
$num == $num2; // returns true
$num === $num2; // returns false because $num is a string and $num2 is an integer
$a !== $b TRUE if $a is not equal to $b, or they are not of the same type
Please Refer to http://php.net/manual/en/language.operators.comparison.php
You can find the info here: http://www.php.net/manual/en/language.operators.comparison.php
It's scarce because it wasn't added until PHP4. What you have is fine though, if you know there may be a type difference then it's a much better comparison, since it's testing value and type in the comparison, not just value.
Is there a difference between !== and != in PHP?
The != operator compares value, while the !== operator compares type as well.
That means this:
var_dump(5!="5"); // bool(false)
var_dump(5!=="5"); // bool(true), because "5" and 5 are of different types
!= is the inverse of the == operator, which checks equality across types
!== is the inverse of the === operator, which checks equality only for things of the same type.
!= is for "not equal", while !== is for "not identical". For example:
'1' != 1 # evaluates to false, because '1' equals 1
'1' !== 1 # evaluates to true, because '1' is of a different type than 1
!== checks type as well as value, != only checks value
$num = 5
if ($num == "5") // true, since both contain 5
if ($num === "5") // false, since "5" is not the same type as 5, (string vs int)
=== is called the Identity Operator. And is discussed in length in other question's responses.
Others' responses here are also correct.
Operator != returns true, if its two operands have different values.
Operator !== returns true, if its two operands have different values or they are of different types.
cheers
See the PHP type comparison tables on what values are equal (==) and what identical (===).
I have been programming in PHP for a while but I still dont understand the difference between == and ===. I know that = is assignment. And == is equals to. So what is the purpose of ===?
It compares both value and type equality.
if("45" === 45) //false
if(45 === 45) //true
if(0 === false)//false
It has an analog: !== which compares type and value inequality
if("45" !== 45) //true
if(45 !== 45) //false
if(0 !== false)//true
It's especially useful for functions like strpos - which can return 0 validly.
strpos("hello world", "hello") //0 is the position of "hello"
//now you try and test if "hello" is in the string...
if(strpos("hello world", "hello"))
//evaluates to false, even though hello is in the string
if(strpos("hello world", "hello") !== false)
//correctly evaluates to true: 0 is not value- and type-equal to false
Here's a good wikipedia table listing other languages that have an analogy to triple-equals.
It is true that === compares both value and type, but there is one case which hasn't been mentioned yet and that is when you compare objects with == and ===.
Given the following code:
class TestClass {
public $value;
public function __construct($value) {
$this->value = $value;
}
}
$a = new TestClass("a");
$b = new TestClass("a");
var_dump($a == $b); // true
var_dump($a === $b); // false
In case of objects === compares reference, not type and value (as $a and $b are of both equal type and value).
The PHP manual has a couple of very nice tables ("Loose comparisons with ==" and "Strict comparisons with ===") that show what result == and === will give when comparing various variable types.
It will check if the datatype is the same as well as the value
if ("21" == 21) // true
if ("21" === 21) // false
=== compares value and type.
== doesn't compare types, === does.
0 == false
evaluates to true but
0 === false
does not
Minimally, === is faster than == because theres no automagic casting/coersion going on, but its so minimal its hardly worth mentioning. (of course, I just mentioned it...)
It's a true equality comparison.
"" == False for instance is true.
"" === False is false
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php == vs === operator
What's the difference between !== and != in PHP?
!== is strict not equal and which does not do type conversion
!= is not equal which does type conversion before checking
=== AND !== checks if the values compared have the same type (eg: int, string, etc.) and have the same values
While...
== AND != only compares the values
"1" != 1 // False
"1" !== 1 // True
It's a type thing. !== takes into account the types of its operands, while != does not (the implicit conversion makes the first conditional false).
== is only true if the values are equal.
=== is only true if the values and types are equal.
the triple equal also make sure the two variable are from the same type
1 == `1` // is ok
1 === `1` // is not same.
Both are comparion operators
$a !== $b Return TRUE if $a is not equal to $b, or they are not of the same type.
$a != $b Return TRUE if $a is not equal to $b.