Aceste structuri permit definirea unei conditii si apoi executarea unor operatii functie de raspuns.
Vom discuta despre:
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if este instructiunea conditionala cea mai folosita avand urmatoarea sintaxa:
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Conditia este incadrata de paranteze rotunde iar instructiunea care se executa in cazul in care conditia este indeplinita intre acolade. Neindeplinirea conditiei face sa se execute ce urmeaza dupa inchiderea acoladei.
Exemplu: se compara doua variabile si se afiseaza un mesaj
PHP Code:
<?php
$a=4;
$b=3;
echo "$a=4<br>";
echo "$b=3<br>";
if ($a>$b) {
echo "$a>$b";
}
?>
else este alta instructiunea conditionala care indica ce se executa in cazul in care conditia mentionata in instructiunea if nu este indeplinita si are sintaxa:
Code:
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Exemplu: se compara doua variabile si se afiseaza un mesaj
PHP Code:
<?php
$a=2;
$b=9;
echo "$a=2<br>";
echo "$b=9<br>";
if ($a>$b) {
echo "$a>$b";
} else {
echo "$a<$b";
}
?>
elseif este o combinatie intre if si else. In cazul in care conditia if nu este indeplinita se introduce elseif care testeaza inca o conditie. Daca nu este indeplinita a doua conditie se executa declaratia introdusa prin else.
Code:
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Exemplu:
PHP Code:
<?php
$a=19;
$b=23;
if ($a<$b) {
echo "$a<$b";
} elseif ($a==$b) {
echo "$a==$b";
} else {
echo "$a>$b";
}
?>
switch este asemanatoare functiei if dar conditia are mai mult de doua valori.
Exemplu: transforma numarul zilei in numele ei
PHP Code:
<?php
$ziua=2;
echo $ziua;
echo "<br>";
switch ($ziua) {
case 1:
echo "Luni";
break;
case 2:
echo "Marti";
break;
case 3:
echo "Miercuri";
break;
case 4:
echo "Joi";
break;
case 5:
echo "Vineri";
break;
case 6:
echo "Sambata";
break;
case 7:
echo "Duminica";
break;
}
?>
while este o instructiune de tip bucla. Atat timp cat conditia este adevarata se repeta bucla.
Exemplu:
PHP Code:
<?php
$numar=1;
while ($numar<=7) {
echo $numar."<br>";
$numar++;
}
?>
for este o instructiune de tip bucla.
Code:
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expresia1 este evaluata la inceputul buclei
expresia2 se verifica la inceputul fiecarei iteratii
expresia3 se executa la sfarsitul fiecarei iteratii
constructia for poate functiona si fara una sau toate aceste expresii
Exemplu: se initializeaza variabila i cu valoarea 1, se verifica daca este mai mica sau egala cu 10 iar apoi se incrementeaza. La fiecare iteratie se tipareste variabila i.
PHP Code:
<?php
for ($i=1; $i<=10; $i++) {
echo $i."<br>";
}
?>
foreach este o constructie care functioneaza doar cu matrice generand erori cand sunt folosite variabile cu tipuri de date diferite sau variabile neinitializate. Sintaxa folosita este:
Code:
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Exemplu:
PHP Code:
<?php
$personal = array(
"Florin" => director,
"Catalin" => inginer,
"Mihai" => economist,
"Sorin" => sofer,
"Diana" => secretara
);
foreach ($personal as $nume => $meserie) {
echo "$nume => $meserie<br>";
}
?>
include si require sunt doua functii asemanatoare folosite pentru includerea in paginile php a unor fisiere externe. Diferenta intre cele doua functii consta in faptul ca daca include da gres scriptul genereaza o avertizare dar functioneaza in continuare in timp ce la require se termina executarea scriptului.
include "fisier1.php";
require "fisier2.html";
break opreste fortat executia structurilor for, foreach, while, do..while sau switch.
break accepta optional un argument numeric care indica numarul de structuri imbricate a caror functionare este oprita.
Exemplu: la i=6 se opreste executia buclei
PHP Code:
<?php
for ($i=0; ;$i++) {
if ($i>6) {
break;
}
echo $i."<br>";
}
?>
continue sare peste restul din iteratia buclei curente si continua executia la inceputul iteratiei urmatoare
continue accepta optional un argument numeric care indica numarul de bucle care vor fi sarite pana la sfarsit.
Exemplu: sare executia peste i==5
PHP Code:
<?php
for ($i=0;$i<8;$i++) {
if ($i==5)
continue;
echo $i."<br>";
} ?>
return
Daca este chemata din interiorul unei functii declaratia return() opreste imediat executia functiei curente si furnizeaza argumentul ca valoare a functiei.
Daca este chemata in scop global executia scriptului curent se opreste.