PHP If Single or Double Equals

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.

A php if statement with one equal sign...? What does this mean?

It's a form of shorthand, which is exactly equivalent to this:

$confirmation = $payment_modules->confirmation();
if ($confirmation) {

}

The 3 different equals

You have = the assignment operator, == the 'equal' comparison operator and === the 'identical' comparison operator.

$a = $b     Assign      Sets $a to be equal to $b.
$a == $b    Equal       TRUE if $a is equal to $b.
$a === $b   Identical   TRUE if $a is equal to $b, and they are of the same type. (introduced in PHP 4)

For more info on the need for == and ===, and situations to use each, look at the docs.

Three equals signs in php comparison

The easiest way to see it, is that == checks equality and === checks identicality. Equality will check the value, but identicality will check the variable type too.

Examples:

var_dump('true' == true); // bool(true)
var_dump('true' === true); // bool(false)

Using one equals sign in an if statement

PHP, like also C, allows to write any expression into an if-condition.

This can be an expression like:

if(!$db=new database()) die("NO DATABASE CONNECTION");

But it has rather the background that the expression $a="abc" is evaluated a different way:

1. Set the value of $a to abc
2. Rest of the expression is: if($a)
3. $a is != 0, so it is true MOST IMPORTANT
4. Expression is true, go into if-case

So the expression is evaluated to if(true) because the priority table of
operators make the expression succeed. It is not a mistake of PHP, it is
rather the definition of TRUE/FALSE and how things get evaluated.

This can also be used in loops like shown in another answer for the loop expression with $db->fetch()

Wordpress foreach if statement shows all users where only one is expected?

My guess is that you're using a single equals (=) instead of a double equals (==) to check the person's instrument. A single equals (=) signifies an assignment, and it returns true if the assignment worked. I think you want to use a double equals (==) to instead check if $user->instrument is the same as Tenorsaxofon.

If this is the case, you'll want to change this:

if ( $user->instrument = 'Tenorsaxofon' )

To this:

if ( $user->instrument == 'Tenorsaxofon' )

(More about that here).

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It also could be that $subscribers contains two users who have their instrument set to Tenorsaxofon. If there's two subscribers with the same instrument, then your echo will print Tenorsaxofon twice, resulting in TenorsaxofonTenorsaxofon

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