Examples explaining common PHP syntax applications_PHP tutorial

Common PHP syntax 1, PHP script code tags

PHP script is a pair of special tags in the file The included content, such as ASP is "<%....%>" and PHP can be seen as "".

However, in order to adapt to the XML standard to embed PHP into XML or XHTML, PHP does not recommend using the short form "" and recommends using the long form tag ""

In addition, the PHP code block also supports the tag form of .

PHP common syntax 2, PHP command delimiter

Each statement in 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.

So, the format of a PHP script can be as follows:

//Note that the last line does not need a semicolon
?>

Common PHP syntax three, PHP comments

PHP multi-line comments use ""

Single-line comments use "#" or "//"

Common PHP syntax 4, PHP output

In ASP, use "<%=...%>" to quickly output a single line, or use "< %Response.Write("...")%>"

Use "echo()" or "print()" directly in PHP, for example:

<ol class="dp-xml"><li class="alt"><span><span class="tag"><</span><span> ?php  </span></span></li><li><span>echo "a";  </span></li><li class="alt"><span>echo (b);  </span></li><li><span>echo ("c");  </span></li><li class="alt"><span>echo d;  </span></li><li><span class="tag">?></span><span>  </span></span></li></ol>

The output is "abcd", and all the above four types can be output normally.

But this is impossible in ASP, especially echo "a"; and echo d; both output as strings themselves. This requires understanding PHP variable definitions.

PHP common syntax 5, PHP variables

Like ASP, PHP variables do not need to be defined first and can be used directly. The type of the variable is automatically generated when assigning a value.

Various variables in PHP are distinguished by adding "$" before the variable name.

<ol class="dp-xml"><li class="alt"><span><span class="tag"><</span><span> ?php  </span></span></li><li><span>$</span><span class="attribute">a</span><span>=</span><span class="attribute-value">"123"</span><span>;  </span></li><li class="alt"><span>echo a;  </span></li><li><span>echo $a;  </span></li><li class="alt"><span class="tag">?></span><span>  </span></span></li></ol>

Input as "a123"

PHP common syntax 6, the difference between single quotes and double quotes in PHP

<ol class="dp-xml"><li class="alt"><span><span class="tag"><</span><span> ?php  </span></span></li><li><span>$</span><span class="attribute">a</span><span>=</span><span class="attribute-value">"123"</span><span>;  </span></li><li class="alt"><span>echo "$a";  </span></li><li><span>echo '$a';  </span></li><li class="alt"><span class="tag">?></span><span>  </span></span></li></ol>

The output is "123$a", where echo "$a" outputs the value of variable a, and echo '$a' outputs the string itself in single quotes.

<ol class="dp-xml"><li class="alt"><span><span class="tag"><</span><span> ?php  </span></span></li><li><span>$</span><span class="attribute">a</span><span>=</span><span class="attribute-value">"123"</span><span>;  </span></li><li class="alt"><span>echo "$a'$a'";  </span></li><li><span class="tag">?></span><span>   </span></span></li></ol>

then the output is "123'123'" and 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 are in double quotes, they will be replaced; while those in single quotes will not be replaced.

If the content in double quotes needs to be escaped, use the "" prefix, such as "", "$", """. So to enter "123$a", it is

<ol class="dp-xml"><li class="alt"><span><span class="tag"><</span><span> ?php  </span></span></li><li><span>$</span><span class="attribute">a</span><span>=</span><span class="attribute-value">"123"</span><span>;  </span></li><li class="alt"><span>echo "$a$a";  </span></li><li><span class="tag">?></span><span>  </span></span></li></ol>

Another example:

<ol class="dp-xml"><li class="alt"><span><span class="tag"><</span><span> ?php  </span></span></li><li><span>$</span><span class="attribute">a</span><span>=</span><span class="attribute-value">"123"</span><span>;  </span></li><li class="alt"><span>echo "$a$a"";  </span></li><li><span class="tag">?></span><span>  </span></span></li></ol>

The output is "123$a"".

What you need to pay attention to when transferring from ASP to PHP is:

1. It is easy to forget to write the separator comma ";".

2. Definition and use of variables.

3. The usage of single quotes and double quotes.

http://www.bkjia.com/PHPjc/446015.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/446015.htmlTechArticlePHP common syntax 1, PHP script code tag PHP script is the content included in a pair of special tags in the file, For example, ASP is %....%, PHP can be seen as ?...?. However, in order to adapt to the XML standard, P...