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Before the misinformation train goes too far out of the station, there are a bunch of things you need to understand about PHP short tags.
The primary issue with PHP's short tags is that XML managed to choose a tag (<?) that was already used by PHP.
With the option enabled, you weren't able to raw output the xml declaration without getting syntax errors:
<?xml version="1.0" encoding="UTF-8" ?>
This is a big issue when you consider how common XML parsing and management is.
What about <?=?
Although <? causes conflicts with xml, <?= does not. Unfortunately, the options to toggle it on and off were tied to short_open_tag, which meant that to get the benefit of the short echo tag (<?=), you had to deal with the issues of the short open tag (<?). The issues associated with the short open tag were much greater than the benefits from the short echo tag, so you'll find a million and a half recommendations to turn short_open_tag off, which you should.
With PHP 5.4, however the short echo tag has been re-enabled separate from the short_open_tag option. I see this as a direct endorsement of the convenience of <?=, as there's nothing fundamentally wrong with it in and of itself.
The problem is that you can't guarantee that you'll have <?= if you're trying to write code that could work in a wider range of PHP versions.
ok, so now that that's all out of the way
Should you use <?=?
Dusting off my PHP hat
I'd definitely favor the use of <?= $someVar ?> over the more verbose echo (simply personal preference). The only downside AFAIK is for users who are running pre-5.4.0, in which case short_open_tag must be enabled in php.ini.
Now having said that, if your project isn't OS, then it's a moot point. If it is, I'd either document the fact that short_open_tags must be enabled, or use the more portable of the two solutions.
This is well documented. From the PHP Manual:
The closing tag of a PHP block at the end of a file is optional, and in some cases omitting it is helpful when using include() or require(), so unwanted whitespace will not occur at the end of files, and you will still be able to add headers to the response later. It is also handy if you use output buffering, and would not like to see added unwanted whitespace at the end of the parts generated by the included files.
Omitting the closing tag helps you prevent accidental whitespace or newlines from being added to the end of the file.
That's a core PHP feature: unlike other languages, you need to tag PHP code with a special tag (normally <?php) because everything else is considered literal output:
This is not PHP
<?php
echo 'This is PHP' . PHP_EOL;
?>
This is not PHP either
D:\tmp>php test.php
This is not PHP
This is PHP
This is not PHP either
Although the manual mentions HTML, PHP doesn't really know/care what content-type is outside its tags.
If you forget to close a PHP block when further stuff follows you normally get a syntax error:
This is not PHP
<?php
echo 'This is PHP' . PHP_EOL;
This is not PHP either
D:\tmp>php test.php
PHP Parse error: syntax error, unexpected 'is' (T_STRING) in D:\tmp\borrame.php on line 6
Blank lines are a sort of special case because they are valid and almost invisible in almost all languages (PHP, HTML, CSS, JavaScript...) so they often unnoticed.
Once you've removed the ?> tag, your literal blank lines have disappeared from the script output because they've become part of the PHP code (and, as such, they've started to get ignored).
Of course, blank lines are ignored by PHP but not necessarily by whatever you are generating which, as I said, does not need to be HTML: it can be a picture, a PDF document, an Excel spreadsheet. Bogus white lines can be easily avoided by not closing the last PHP block when it's the last part of the file.
Set
short_open_tag=On
in php.ini
And restart your Apache server.
This can be done by enabling short_open_tag in php.ini:
short_open_tag = on
If you don't have access to the php.ini you can try to enable them trough the .htaccess file but it's possible the hosting company disabled this if you are on shared hosting:
php_value short_open_tag 1
For the people thinking that short_open_tags are bad practice as of php 5.4 the <?= ... ?> shorttag will supported everywhere, regardless of the settings so there is no reason not to use them if you can control the settings on the server. Also said in this link: short_open_tag