Here is some example code:
$headers = 'From: [email protected]' . "\r\n" .
'Reply-To: [email protected]' . "\r\n" .
'X-Mailer: PHP/' . phpversion();
What does the period character do in the middle of each piece of the string?
For example,
"blabla" . "blabla" . "blablalba";
It's the concatenation operator, concatenating both strings together (making one string out of two separate strings).
the " . = " operator is a string operator, it first converts the values to strings; and since " . " means concatenate / append, the result is the string " 120 ".
In PHP, the period is the concatenation operator. Putting the periods in tells PHP to concatenate "mod/" to $modarrayout and then concatenate the resulting string to "/bar. php" . See page String Operators.
Alternatively referred to as a full stop or dot, a period ( . ) is a punctuation mark commonly found on the same US QWERTY keyboard key as the greater than ( > ).
This operator is used to combine strings.
EDIT
Well, to be more specific if a value is not a string, it has to be converted to one. See Converting to a string for a bit more detail.
Unfortunately it's sometimes mis-used to the point that things become harder to read. Here are okay uses:
echo "This is the result of the function: " . myfunction();
Here we're combining the output of a function. This is okay because we don't have a way to do this using the standard inline string syntax. A few ways to improperly use this:
echo "The result is: " . $result;
Here, you have a variable called $result
which we can inline in the string instead:
echo "The result is: $result";
Another hard to catch mis-use is this:
echo "The results are: " . $myarray['myvalue'] . " and " . $class->property;
This is a bit tricky if you don't know about the {}
escape sequence for inlining variables:
echo "The results are: {$myarray['myvalue']} and {$class->property}";
About the example cited:
$headers = 'From: [email protected]' . "\r\n" .
'Reply-To: [email protected]' . "\r\n" .
'X-Mailer: PHP/' . phpversion();
This is a bit tricker, because if we don't use the concatenation operator, we might send out a newline by accident, so this forces lines to end in "\r\n" instead. I would consider this a more unusual case due to restrictions of email headers.
Remember, these concatenation operators break out of the string, making things a bit harder to read, so only use them when necessary.
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