arr.join(';')

var arr = ["array1","array2","array3"];
var strr = "";
for(let i=0;i<arr.length;i++){

if(i!=arr.length-1){
    strr+=arr[i]+";";
}else{
    strr+=arr[i];
}

}
console.log(strr);

["array1","array2","array3"].join(";")

["array1","array2","array3"].join(';')

用implode啊,implode(";",$arr);