10.21 a.m. PHP Basics

The new PHP file must be placed in the WWW folder under the Wamp installation directory. If you get somewhere else, PHP will not work and an error is displayed.

<? php?>  //How to embed PHP

 <? php//The beginning of the way to embed PHP  //php single-line      comment syntax  /*   php multiline comment syntax         */ //  output syntax//echo "Hello"; the most common is Echo,echo followed by a string.    The principle is to use PHP code in the source code to play Hello, and then through the browser parsing out. echo "World", "dhakj"; You can output multiple strings, separated by commas.        <br/> (The contents of the Web page), instead of \ n, is required for line breaks. print "AAA"; can also be output, but only one string//print_r () is output; An array is written in parentheses to print the group//var_dump ();        can also be output, but the output is variable and type, which is most powerful relative to the output above.    Variable definition//data type, weakly typed language, defined without the need to define the variable type, automatic turn. $a = "Hello", defined as $ A, and all variables are the beginning of the $ symbol. Even for the For Loop for ($i =1; $i <10; $i + +) also add $.        
//$hello = "World"; echo $ $a; Variable variable, the result of the output is world.        Parse $a=hello First, then parse $hello=world.    Type conversion//$a = 6; $b = (string) $a; Type conversions, converting integers to strings. (string) $a means converting an integer A to a data type of string. 

Settype ($a, "string"); Another way
Var_dump ($a);
　　
Operators and expressions, mathematical operators (+ 、-、 *,/) and JS inside the same.
$a = 6;
$b = 7;
Echo $a + $b

$c = $a = = $b;
Var_dump ($c);

Concatenation of strings
$a = "Hello";
$b = "World";
$c = $a. $b; PHP inside the concatenation of strings with a dot (.) Other languages are used by the +.
Echo $c; The output is HelloWorld

$a = 8;
@ $c = $a/$b; The error suppressor, which masks the wrong information. Generally not used, there is the wrong information to correct instead of shielding off.
Echo $c;

　　
The error message inside PHP can be masked with @. Notice and warning can be blocked off.
Notice: Reminders
Warning: Warning
Error: Wrong

Ternary operator, which is equivalent to a simple if.
$a = 4;
$b = 5;
echo $a = = $b? " Equal ":" Not Equal "; Equality outputs "equal", unequal outputs "unequal", and the middle is separated by colons.

Statement
order, executed in order.
$a = 5;
$b = 6;
　　
　　
Branch, the first is if, and the second is switch 
/ *if ($a = = $b)
{
echo "equal";
}
Else
{
echo "Unequal";
}

Switch ($a)
{Case 4:
echo "4444";
Break
Case 5:
echo "55555";
Break
Case 6:
echo "66667";
Break
Default
echo "000000";
}*/ 


//loops, for loops, while loops, Do,while loops
/ *For ($a =0; $a <10; $a + +)
{
echo $a;
}
　　
while (true)//to judge the condition before execution
{
echo "AAA";
}

Do//Execute the statement first, then look at the condition.
{
}
while ()*/?>

10.21 a.m. PHP Basics