This question already has answers here:
What is the difference between single-quoted and double-quoted strings in PHP?
(7 answers)
Closed 8 years ago.
in HTML
we can
face='Tahoma'
face="Tahoma"
and in PHP
$name = "Junaid";
$name = 'Junaid';
$names = array('Junaid','Junaid','Junaid');
$names = array("Junaid","Junaid","Junaid");
now all these statements are correct with single or double quotes but
what difference does it make
which is the preferred method
what types of quotes to use where
which one of the following is correct
$link = "www.anyLINK.com"
echo "<a href=' ". $link ." '>Click Here</a>"
echo "<a href= ". $link ." >Click Here</a>"
The difference between single and double quotes in PHP is that PHP will read variables inside of double quotes but not single. For example:
<?php
$variable = "test";
echo "Can you see this $variable"; // Can you see this test
echo 'Can you see this $variable'; // Can you see this $variable
?>
The single quote will be read literal, where was double will attempt to replace the $variable with it's value.
Optimization Differences
As pointed out in the comments below, single quotes tend to be faster than double. In a quick benchmark, double quotes with any $'s escaped is the fastest vs single and double with and without $variables in the string. See http://codexon.codepad.org/54L3miwN
See http://php.net/manual/en/language.types.string.php.
In particular, variables are expanded in double quotes:
$foo = 42;
print('foo is $foo'); // foo is $foo
print("foo is $foo"); // foo is 42
In HTML, it doesn't matter at all.
In PHP, it does. Using the single-quotes prevents variables from being interpreted; for instance, echo '$foo'; will print "$foo". Not the variable, just the characters. Also, you have to escape single-quotes within single-quotes, but not single-quotes within double-quotes, etc. I answered this question before here.
As for your second question, they're both wrong. It should be:
echo "<a href='". $link ."'>Click Here</a>"
or, better yet:
echo "<a href='$link'>Click Here</a>"
or, better still, a templating engine like Smarty TPL.
Related
I would like to replace array string values which contains multiple special characters to normal one.
Tried Code (array values):
$data['ENV_TEST'] = "rambo";
$data['ENV_DEV'] = "Project Bribara<"${ENV_TEST}"#gmail.com>"
echo str_replace("${ENV_TEST}", $data['ENV_DEV'], $data['ENV_DEV']);
also tried
echo str_replace("\"${ENV_TEST}\"", $data['ENV_DEV'], $data['ENV_DEV']);
Expected:
"Project Bribara<rambo#gmail.com>"
Actual:
"Project Bribara<"${ENV_TEST}"#gmail.com>"
How can I get the expected output?
You should on PHP strings sometime. The important part about double quoted strings for your question is that you need to put a backslash before every $ and every " inside your string. Your code will then look like this:
$data['ENV_TEST'] = "rambo";
$data['ENV_DEV'] = "Project Bribara<\"\${ENV_TEST}\"#gmail.com>";
echo str_replace("\${ENV_TEST}", $data['ENV_TEST'], $data['ENV_DEV']);
//also tried
echo "\n\n";
echo str_replace("\"\${ENV_TEST}\"", $data['ENV_TEST'], $data['ENV_DEV']);
If you use single quoted strings you don't need to escape $ (see the manual), and instead of \", you would need to escape single quotes (but there aren't any in your example).
$data['ENV_TEST'] = "rambo";
$data['ENV_DEV'] = 'Project Bribara<"${ENV_TEST}"#gmail.com>';
echo str_replace("\${ENV_TEST}", $data['ENV_TEST'], $data['ENV_DEV']);
//also tried
echo "\n\n";
echo str_replace('"${ENV_TEST}"', $data['ENV_TEST'], $data['ENV_DEV']);
I also fixed a missing semicolon and replaced DEV with TEST in one place.
String concatenation in PHP is done through the . operator. Your code would be:
$data['ENV_DEV'] = "Project Bribara<".$data['ENV_TEST']."#gmail.com>"
Let's say this is my script down here, as you can see I've used multiple " and '. These quotations conflict in ending the current php variable, so it basically sees this:
$message = "<?php echo '<div class="
As a string, whilst the quotation is only to define the class, not to end the variable. I've tried using ' but then it conflicts with the echo, so I'm kinda stuck at the moment.
<?php
$message = "
<?php
echo '<div class="gebruiker">';
$fh = fopen('_gebruiker.txt','r');
while ($line = fgets($fh)) {
echo($line);
}
fclose($fh);
echo '</div>';
?>
";
**MORE PHP CODE HERE**
?>
How can I use multiple quotations in one PHP script without them having conflicts.
If you use single quotes outside, you need to escape all single quotes inside, but can use double quotes and the dollar char without escaping.
If you use double quotes outside, you need to escape all double quotes and dollar chars inside, but can use single quotes without escaping.
If you use a heredoc string, you need to escape dollar chars but can use both single and double quotes without escaping.
If you use a nowdoc string, you do not need to escape anything unless you have FOO; in the string at the beginning of a new line.
So the solution is to use a nowdoc string:
$message = <<<'EOF'
your stuff with " or ' or $ here!
EOF;
Adding a backslash so PHP can recognize just only double quotes or quotes when escaped.
Example:
echo "<div class=\"gebruiker\">";
I suggest using either Heredoc or Nowdoc
Example
$foo = 'test';
// Heredoc
$here = <<<HERE
I'm here, $foo!
HERE;
// Nowdoc
$now = <<<'NOW'
I'm now, $foo!
NOW;
Heredoc will print the contents of $foo when echoed while Nowdoc will simply echo $foo.
In the references I added below you can do more reading up on this subject.
References:
php.net - strings
stackoverflow - advantages of heredoc vs nowdoc
You can escape the quotes with a slash character like so: \"
This should work, you can't open Php tag without closing before.
<?php
$message = '<div class="gebruiker">';
$fh = fopen('_gebruiker.txt','r');
while ($line = fgets($fh)) {
$message .=$line.'<br/>';
}
fclose($fh);
$message.='</div>';
echo $message;
**MORE PHP CODE HERE**
?>
This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
Difference between single quote and double quote string in php
I am new to PHP and in programming i have seen use of both "" and ' '.
What is the difference between "" and ' '?
And in declaring a link i have used the following ,but it does not seem to work there must be something wrong in quotation:
$abc_output .='' Back to Main Menu'';
echo $abc_output;
What might be the error here?
You want to keep the text inside of your string:
$abc_output .='Back to Main Menu';
The difference between ' and " is that you can embed variables inside of a double quoted string.
For example:
$name = 'John';
$sentence = "$name just left"; // John just left
If you were to use single quotes, then you'd have to concatenate:
$name = 'John';
$sentence = $name.' just left'; // John just left
PS: Don't forget that you always have to escape your quotes. The following 2 are the same:
$double = "I'm going out"; // I'm going out
$single = 'I\'m going out'; // I'm going out
Same applies the other way around:
$single = 'I said "Get out!!"'; // I said "Get out!!"
$double = "I said \"Get out!!\""; // I said "Get out!!"
Double quotes allow additional expressions, such as "$variable \n", which single quotes don't. Compare:
$variable = 42;
echo "double: $variable,\n 43\n";
echo 'single: $variable,\n 43';
This outputs:
double: 42,
43
single: $variable,\n 43
For more information, refer to the official documentation.
Text in double quotes are parsed.
For example:
$test = 'something';
print('This is $test');
print("This is $something");
would result in:
This is $test
This is something
If you don't need the string to be parsed you should use single quotes since it's better performance wise.
In your case you need to do:
$abc_output .='Back to Main Menu';
echo $abc_output;
Or you will get an error.
The Back to Main Menu wasn't in the string.
This question already has answers here:
Closed 12 years ago.
Possible Duplicate:
Difference between single quote and double quote string in php
Hi all
I am very new to PHP and I wanted to know what is the difference in use of ' ' and " " ?
Thanks
$name='RkReddy';
echo "$name hi hello"; //op-RkReddy hi hello
echo '$name hi hello';//op-$name hi hello
Double quotes evaluate the content of the string, the single quotes don't.
$var = 123;
echo 'This is the value of my var: $var'; // output: This is the value of my var: $var
echo "This is the value of my var: $var"; // output: This is the value of my var: 123
It WAS a perfomance issue too, 'cause evaluation time affects the interpreter, but nowadays with the current (minimum) hardware it's not an issue anymore.
Nothing much, but when using double quotes you can use a PHP variable inside the string, and the string will output the variable's value. When using a single quote it will output the variable's name without parsing the actual value. IE.:
$something = "A nice little variable";
echo "$something is printed out"; //output: A nice little variable is printed out
echo '$something is not printed out'; //output: $something is not printed out
Hope this helps!
simple problem baffling me...
i have a function:
function spitHTML() {
$html = '
<div>This is my title</div>\n
<div>This is a second div</div>';
return $html
}
echo $spitHTML();
Why is this actually spitting out the \n's?
Backslashes used in single quote strings do not work as escape characters (besides for the single quote itself).
$string1 = "\n"; // this is a newline
$string2 = '\n'; // this is a backslash followed by the letter n
$string3 = '\''; // this is a single quote
$string3 = "\""; // this is a double quote
So why use single quotes at all? The answer is simple: If you want to print, for example, HTML code, in which naturally there are a lot of double quotes, wrapping the string in single quotes is much more readable:
$html = '<div class="heading" style="align: center" id="content">';
This is far better than
$html = "<div class=\"heading\" style=\"align: center\" id=\"content\">";
Besides that, since PHP doesn't have to parse the single quote strings for variables and/or escaped characters, it processes these strings a bit faster.
Personally, I always use single quotes and attach newline characters from double quotes. This then looks like
$text = 'This is a standard text with non-processed $vars followed by a newline' . "\n";
But that's just a matter of taste :o)
Because you're using single quotes - change to double quotes and it will behave as you expect.
See the documentation for Single quoted strings.
Change ' to " :) (After that, all special chars and variable be noticed)
$html = "
<div>This is my title</div>\n
<div>This is a second div</div>";