PHP input and output

PHP uses forms to accept data, echo output data, and $ to define variables.

<?php echo $_post["Sub"]; Post is the name of the form?><formAction=""Method= "POST"> <!--The action is the address of the receiving form, and if it is empty, it is received on the current page and method is the -<inputtype= "text"name= "Sub"/><inputtype= "Submit"value= "Submit" />   <!--Submit Refresh Page -</form> <!--The program flow is: First go through PHP, when the post is empty, then walk the form form, write data, after submission, refresh the page, the post received data displayed in the new page -

Example 1. Summing sum

<formAction=""Method= "POST"><inputtype= "text"name= "a" /><inputtype= "Submit"value= "Calculation" /></form><?php$n=$_post[' a ']; $sum; for ($i =1; $i <= $n; $i + +) {$sum + = $i;} echo $sum;?>

Example 2: Finding the sum of factorial and factorial

<formAction=""Method= "POST"><inputtype= "text"name= "B" /><inputtype= "Submit"value= "Calculation" /></form><?Php$s=1, $sum =0, $n =$_post[' B '];for ($i =1; $i <= $n; $i + +) {$s *= $i; $sum + = $s;} echo "factorial is $s, factorial sum is $sum";?>

Example 3. List of prime numbers within 100

<? phpfor ($i =2; $i <=100; $i + +) {    $k =0;    for ($j =2; $j <= $i; $j + +)    {        if ($i% $j ==0)        {            $k + +;                }            }    if ($k ==1)    {        echo $i; echo "&nbsp;"}    } ?>

Example 4. Finding the root of the ax^2+bx+c=0 of a unary two-time equation

<formAction=""Method= "POST">Please enter the value of a<inputtype= "text"name= "a" />Please enter the value of B<inputtype= "text"name= "B" />Please enter a value for C<inputtype= "text"name= "C" />  <inputtype= "Submit"value= "Calculation" /></form><?php$a=$_post[' a ']; $b =$_post[' B ']; $c =$_post[' C ']; $de = ($b * $b -4* $a * $c); if ($a ==0) {echo "This equation is not a two-time equation!). Re-enter"; }else{echo "This equation is a unary two-time equation!";        echo "<br/>";        if ($de >=0) {$x 1= (-$b +sqrt ($de))/($a);        $x 2= (-$b-sqrt ($de))/($a);            if ($de >0) {echo "This equation has two different real roots"; echo "<br/>"; echo "x1= $x 1"; echo "&nbsp;";        echo "x2= $x 2";            } else {echo "This equation has two identical real roots"; echo "<br/>";        echo "x1=x2= $x 1";    }} else {echo "This equation has no real roots!"; }    }?>

Example 5: Enter gender, height, weight to see if it is a standard weight

<formAction=""Method= "POST">Please enter gender<inputtype= "text"name= "B"  />Please enter height (cm)<inputtype= "text"name= "C"/>Please enter weight (kg)<inputtype= "text"name= "D" /><inputtype= "Submit"value= "Submit" /></form><?php$b=$_post[' B ']; $c =$_post[' C '); $d =$_post[' d '];if ($b = = "Male") {$n = ($d-$c +100);    if ($n >=-3&& $n <=3) {echo "Your weight is the standard weight";    } else if ($n >3) {echo "You need to lose weight!";    } else {echo "You need to increase nutrition!";    }}else if ($b = = "female") {$n = ($d-$c +110);    if ($n >=-3&& $n <=3) {echo "Your weight is the standard weight";    } else if ($n >3) {echo "You need to lose weight!";    } else {echo "You need to increase nutrition!"; }}else{echo "input wrong!";}?>

Example 6. Enter three numbers, sort from large to small

<formAction=""Method= "POST">Please enter the first number<inputtype= "text"name= "a" />Please enter a second number<inputtype= "text"name= "B" />Please enter a third number<inputtype= "text"name= "C" /><inputtype= "Submit"value= "Sort" /></form><?php $x =$_post[a]; $y =$_post[b]; $z =$_post[c];if ($x < $y) {$zhong = $x;    $x = $y; $y = $zhong;}    if ($x < $z) {$zhong = $x;    $x = $z; $z = $zhong;}    if ($y < $z) {$zhong = $y;    $y = $z; $z = $zhong;} echo $x; echo "&nbsp;"; echo $y; echo "&nbsp;"; Echo $z; ?>

PHP input and output