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I got some PHP code here:
<?php
echo 'hello ' . 1 + 2 . '34';
?>
which outputs 234,
But when I add a number 11 before "hello":
<?php
echo '11hello ' . 1 + 2 . '34';
?>
It outputs 1334 rather than 245 (which I expected it to). Why is that?
970
Prepend and Append Strings in PHPYou can use the concatenation operator . if you want to join strings and assign the result to a third variable or output it. This is useful for both appending and prepending strings depending on their position. You can use the concatenating assignment operator .
Due to this, mixing the StringBuilder and + method of concatenation is considered bad practice. Additionally, String concatenation using the + operator within a loop should be avoided. Since the String object is immutable, each call for concatenation will result in a new String object being created.
If you want to concatenate a string and a number, such as an integer int or a floating point float , convert the number to a string with str() and then use the + operator or += operator.
If you concatenate Stings in loops for each iteration a new intermediate object is created in the String constant pool. This is not recommended as it causes memory issues.
That's strange...
But
<?php
echo '11hello ' . (1 + 2) . '34';
?>
or
<?php
echo '11hello ', 1 + 2, '34';
?>
fixes the issue.
UPDATE v1:
I finally managed to get the proper answer:
'hello' = 0 (contains no leading digits, so PHP assumes it is zero).
So 'hello' . 1 + 2 simplifies to 'hello1' + 2 is 2. Because there aren't any leading digits in 'hello1' it is zero too.
'11hello ' = 11 (contains leading digits, so PHP assumes it is eleven).
So '11hello ' . 1 + 2 simplifies to '11hello 1' + 2 as 11 + 2 is 13.
UPDATE v2:
From Strings:
The value is given by the initial portion of the string. If the string starts with valid numeric data, this will be the value used. Otherwise, the value will be 0 (zero). Valid numeric data is an optional sign, followed by one or more digits (optionally containing a decimal point), followed by an optional exponent. The exponent is an 'e' or 'E' followed by one or more digits.
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