Some basic knowledge for getting started with PHP learning (a must-read for newbies)_PHP Tutorial
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Release： 2016-07-13 17:29:15
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1. PHP script code tags
PHP script is the content included in a pair of special tags in the file. For example, ASP is "<%....%>", PHP It can be seen as "".
However, in order to adapt to the XML standard to embed PHP into XML or Format tag “”In addition, PHP code blocks also support form of marking.
2. PHP command delimiter Each statement of PHP needs to be separated by a semicolon ";", but for the PHP end mark "?> ;", because it automatically implies a semicolon, so there is no need to append a semicolon.
............ ; ............ ;............ */ //Note that the last line can be without a semicolon ? >
3. PHP comments
PHP multi-line comments use "/* .... ..... */" Single-line comments use "#" or "//"
Four, PHP output
echo "a"; echo (b); echo ("c"); echo d; ?>
in ASP Use "<%=...%>" to quickly output a single line, or use "<%Response.Write("...")%>"
Use "echo directly in PHP" ()" or "print()", such as:
echo "a"; echo (b); echo ("c");echo d;?>
will be output as "abcd", and all the above four types can be output normally.
But in ASP , especially echo "a"; and echo d; are both output as strings themselves, which is impossible. This requires understanding PHP variable definitions.
5. PHP variables
$a="123"; echo a; echo $a; ?>
Like ASP, PHP variables can be used directly without defining them first. The type of the variable is automatically generated when assigning a value. Various variables in PHP are preceded by “$” to indicate the difference.
$a="123"; echo "$a"; echo $a; ?>
$a="123";echo a;echo $a; ?>
TBODY>
The input is "a123"
$a="123"; echo "$a$a"; ?>
6. The difference between single quotes and double quotes in PHP
$a="123";echo "$a"; echo $a; ?>
The output is " 123$a
$a="123"; echo "$a$a"; ?>
", where echo "$a" outputs the value of variable a, and echo $a outputs the value in single quotes The string itself.
$a="123";
$a="123"; echo "$a$a""; ?>
echo "$a$a";
?> The output is "123123 " not "123$a". Although it is $a, the variable placed under double quotes is still replaced. So, it can be concluded that: As long as the variables in the content are in double quotes, they will be replaced; while those in single quotes will not be replaced in any way .
If the content in double quotes needs to be escaped, use the "" prefix, such as "", "$", """. So to enter "123$a", it is
$a="123";echo "$a$a";?>
Another example:
$a="123";echo "$a$a"";?>
The output is "123$a"". ASP transfer to PHP requires attention:
1, the separator comma ";" It’s easy to forget to write. 2, definition and use of variables.
3, usage of single quotes and double quotes.
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