PHP learning (4) - data types

PHP supports 8 primitive data types.

Four scalar types: (scalar type is the basic type)

• boolean (Boolean)
• integer (integer)
• float (floating point type, also called double) (Due to historical reasons, float is also It’s called double, there is no distinction between single precision and double precision in PHP)
• string (String type is a scalar type in PHP and a class type in Java)

Two composite types:

• array (array)
• object (object)

Finally there are two special types:

• resource (resource)
• NULL (no type)

The type of the variable is usually not set by the programmer. Exactly, this is determined at runtime by PHP based on the context in which the variable is used.

If you want to check the value and type of an expression, use the var_dump() function.
If you just want a human-readable representation of the type for debugging, use the gettype() function. To check a type, don't use gettype(), use the is_type function.

Example:

<code><span><span><?php </span><span>$a_bool</span> = <span>TRUE</span>;   <span>// a boolean</span><span>$a_str</span>  = <span>"foo"</span>;  <span>// a string</span><span>$a_str2</span> = <span>'foo'</span>;  <span>// a string</span><span>$an_int</span> = <span>12</span>;     <span>// an integer</span><span>$a_float</span> = <span>3.14</span>;  <span>// a float(double)</span><span>echo</span> gettype(<span>$a_bool</span>).<span>"<br>"</span>; <span>// prints out:  boolean</span><span>echo</span> gettype(<span>$a_str</span>).<span>"<br>"</span>;  <span>// prints out:  string</span><span>echo</span> gettype(<span>$an_int</span>).<span>"<br>"</span>;  <span>// prints out:  integer</span><span>echo</span> gettype(<span>$a_float</span>).<span>"<br>"</span>;  <span>// prints out:  double</span><span>// If this is an integer, increment it by four</span><span>if</span> (is_int(<span>$an_int</span>)) {
    <span>echo</span><span>"an_int = "</span>.<span>$an_int</span>.<span>"<br>"</span>;
    <span>$an_int</span> += <span>4</span>;
    <span>echo</span><span>"an_int = "</span>.<span>$an_int</span>.<span>"<br>"</span>;
}

<span>// If $bool is a string, print it out</span><span>// (does not print out anything)</span><span>if</span> (is_string(<span>$a_str</span>)) {
    <span>echo</span><span>"String: $a_str"</span>.<span>"<br>"</span>;
}

<span>echo</span> var_dump(<span>$a_float</span>, <span>$a_bool</span>, <span>$a_str</span>, <span>$an_int</span>);

<span>?></span></span></span></code>

Output:

<code>boolean
<span>string</span>
integer
<span>double</span>
an_int = <span>12</span>
an_int = <span>16</span>
String: foo
<span>float</span>(<span>3.14</span>) <span>bool</span>(<span>true</span>) <span>string</span>(<span>3</span>) <span>"foo"</span><span>int</span>(<span>16</span>)</code>

Explanation of gettype() in the PHP manual (please enlarge to view?):

For the specific use of each type, please refer to the official PHP manual. I am just here Throw a few bricks to attract jade.

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The above introduces PHP learning (4) - data types, including aspects of content. I hope it will be helpful to friends who are interested in PHP tutorials.